YCombinator_logoStartup incubator Y Combinator is hosting its semi-annual Demo Day today. Twice a year, the Mountain View, Calif.-based incubator parades its latest batch of companies onstage to present before potential investors.

This afternoon, 26 companies will pitch their business plans. Approximately half of them have not yet launched. We’ll be in Mountain View to cover the ones that catch our fancy.

Y Combinator companies generally receive about $5,000 plus an additional $5,000 per founder and are relocated to Y Combinator’s Mountain View destination for three months, in return for a 2-10% ownership. The program’s alumni include Loopt, Justin.tv, Weebly and Scribd.

Below are 21 of the companies presenting today that agreed to be mentioned, along with descriptions that they provided. Five others are still in stealth mode, and requested to go unnamed.

Founders: Alex Krupp, Allan Young
LaunchHear is a platform for introducing new & unreleased products to digital influencers. We reduce the cost of sending free products to bloggers and tweeters by 10x. We also host Swagapalooza, the first invitation-only event for only the most-followed bloggers and tweeters from across the country.

Founders: Paul Biggar, Nathan Chong
NewsLabs turns an experienced offline journalist into VentureBeat or TechCrunch for their niche. We provide tools, traffic, monetization and community to allow journalists to succeed as personal brands online, while allowing them to focus on the writing and reporting.

Seeing Interactive
Founders: Lloyd Armbrust, Jason Novek
A white-label Yelp for newspapers: Think Yellow Pages + Cars + Homes + Craigslist all launched as one package for small US markets. We work through local newspapers, TV or Radio stations to brand the product as their own and make money through monthly fees and upsells.

Founder: Chad Etzel
Creating a mobile phone push notification platform which allows any service/business/app/website/anyone to send instant notifications to their users’ mobile phones without the need to develop applications for specific hardware models.

Founders: Jon Dahl, Brandon Arbini, Steve Heffernan
Cloud services for video encoding, delivery, and monetization (AWS for video)

Founders: Thomas Pun, James Black, David Kelso
Nowmov shows you the hottest videos on Twitter RIGHT NOW. We discover the most talked about videos well before our competitors do (YouTube, Redux and Bitly.tv). Our user experience intentionally mimics TV watching — discovery is passive, rather than requiring the user to click around. Videos are presented continuously in an elegant user interface. Users can skip and replay clips at any time just like surfing TV channels.

Founders: Ryan Damico, Bennett Rogers, Peter Lai, Matt Long
Crocodoc makes it easy to collaboratively mark up and share documents online. Our goal is to do to Adobe Acrobat what Gmail did to Outlook: replace a popular desktop application with a better online version.

Founders: Kevin Lacker, Dan Silberman
We make social games. We launch faster, iterate faster, and use metrics better.

Founders: Anson Tsai, Tim Wong
Secondary market for the $100 billion / year gift card market.

Founders: Troy Kruthoff, Robert Bagley, Josh Unfried
Replace your twitter profile page with a custom website. Crowd source and engage content from the tweet stream with language processing technology to automatically identify questions, praise and complaints mentioning your brand. Collaborate with team members, site visitors and twitter users with our embedded multi-account twitter client and CRM. Track results and tweet smarter with built-in analytics and dashboards.

CHROMAom, Inc.
Founders: Darius Monsef, Aaron Epstein, Chris Williams
Profitable and reaching over 1 million visitors per month with the largest color community on the web, we’re positioned to turn our online dominance into a global color authority. In the near future, we see a world where every color – in the products we buy, brands we trust or spaces we live in – will be influenced by CHROMAom.

Founders: Joe Fahrner, Jason Konrad
Answerly has developed a technology and methodology to identify under-served, high value segments of the web search market and rapidly prototype vertical search engines to address these opportunities. Our first product, Answerly.com, is a Q&A search engine that receives nearly 1MM questions per month which we monetize through targeted advertising and referrals to online experts and local service providers.

Founders: Dan Morin, Jeff Morin
The current practice of creating content around a perceived audience interest and attempting to monetize it through potentially unrelated advertising is an inefficient business model. Zenedy is taking the opposite approach by first determining algorithmically what content people are searching for, then identifying what portion of that content could effectively be monetized through targeted advertising, and finally contracting out the creation of that content to qualified freelance writers. This model minimizes the risks associated with creating content based on little or no data, and results in content which quickly pays for itself, and then continues to generate revenue into the foreseeable future.

Data Marketplace
Founders: Matt Hodan, Steve DeWald
Data Marketplace helps people find, buy and sell data online. We are like Amazon.com, but for data. Sellers publish data to Data Marketplace for buyers to purchase and download. We reduce friction between buyers and sellers by (a) making it easier for buyers to find and access the data they need, and (b) offering sellers a more efficient sales and distribution channel than is currently available. In addition to the marketplace, we are developing a number of new technologies that facilitate paid information exchange, including a social data request and fulfillment system and payment gateway for third-party APIs and data feeds.

Founders: Denis Mars, Arend Naylor
Imagine if you as the site owner could make money every time someone played a video (such as YouTube, Vimeo, etc) on your website or blog. Embedster makes this possible.

Founers: Howie Liu, Evan Beard
Etacts is Salesforce for everyone–an individual CRM that keeps track of people and relationships (instead of deals). We also fix the email overload problem by adding social data and previous communication history to your emails and filtering emails by the importance of the sender.

Founders: Sean Creeley, Arthur Gibson
Embedly is a single source for embeddable of content on the web.

Founders: Justin Yoshimura, Hong Hu
500Friends enables online retailers to dramatically increase their brand image, traffic, and sales by effectively leveraging social media. Merchants use our technologies to identify active social networkers and offer them rewards such as discounts, loyalty points, and charitable contributions in exchange for sharing the site with their friends. We’re already generating sales for our existing clients!

Founders: Kovas Boguta, Paulius Jurgutis
Infoharmoni visualizes the real-time social web. We aggregate content, aggregate people, aggregate relationships and then express those visually, in real-time and over time. Our tools visually slice and dice the stream and put that into actionable context by correlating it with business data. This lets marketers demonstrate ROI on today’s most relevant platforms: Twitter, Bit.ly, Gowalla and Foursquare.

Founders: Jason Wilk, Paras Chitakar
140Bets makes social sports (and soon pop culture) betting applications for Twitter, Facebook and Mobile platforms.

Founder: Daniel Gross
Greplin is a search engine that runs through all of your cloud data. Much like Google indexes webpages, Greplin indexes your Facebook, Gmail, Twitter, Basecamp etc data and provides a fast, cross-service full-text search.

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