Posterous, a startup that simplifies the blogging process, has raised $725,000 of new angel funding.

The San Francisco company allows you to write and post blog entries any way you choose — through the web site, through email, or via SMS text message. You don’t have to create an account, or even post on the Posterous site itself. Instead, you can use it as a “middle man” for other blogging services like Blogger, WordPress, and TypePad. Posterous was incubated by Y Combinator, and I thought it was one of the most promising startups to present at Y Combinator’s most recent launch day.

The company is building out its service to match the features you’d expect to see in a standard blogging platform. Today it’s launching a group blog feature, so users can add other email addresses to a Posterous blog, allowing friends and family to post as well. Co-founder Garry Tan tells me that the site will be adding password-protected blogs soon, too.

The angel funding, which Tan has confirmed, was first reported by TechCrunch. The round comes from XG-Ventures and a group of individual angel investors led by Satish Dharmaraj, who co-founded Yahoo-acquired email startup Zimbra. [Update: Other investors include former Netscape CEO Eric Hahn, Mitch Kapor, and Guy Kawasaki.] Combined with the initial backing from Y Combinator, Posterous’ total funding is now $740,000.

Microblogging startup Tumblr, a Posterous competitor, announced a $4.5 million second round earlier this month.