If you’ve never heard of Dragon’s Den, it’s a popular British TV reality series, where entrepreneurs pitch their ideas to get funding from business experts — the “Dragons”. One of those Dragons, Doug Richard, a UK-based Californian and founder of investment research firm Library House got a name for himself as a particularly fastidious investor on the show. And now he’s selected 20 of the UK’s most promising web application start-ups to go and try their luck in Silicon Valley.

The initiative is called Web Mission 2008, and it offers subsidized participation in a one-week tour of the Valley, which begins next week. The program includes visits to Oracle, Bebo and the Web 2.0 Expo. For these British web start-ups, many with CEOs in their twenties, it’s a pretty alluring opportunity. The jury, led by Doug Richard, describe the selected companies as highly promising businesses that are well prepared to attract American investors and customers. “Some of these companies are as good as anything coming out of the Valley”, Richard said in a statement.

More than 100 British web companies applied for the 20 available slots, and the winners were announced the first week of March. The program is sponsored by the UK Trade & Investment Organisation, along with some companies from the private sector. The idea is that British web companies in their early stage have a lot to learn — and earn — from entering the US.

The companies span a broad range of web applications (see full list here). Most were founded a year or two ago. Here’s a quick taste of who’s coming:

There’s the travel social network WAYN (Where Are You Now?), with 11.4 million members but only a small crowd in the US so far. Their service resembles free social networking tools like Dopplr and Twitter but specifically targets travelers. Users keep their travel profiles updated with photos, experiences, and location so that friends at home can track their progress and so they can meet up or trade tips with fellow WAYN traveling similar routes. WAYN currently has 11 employees in London and 35 developers in Poland. It took in $11 million in funding in 2006 from investors including Brent Hoberman who is also the founder of ticket site Lastminute.com.

Another company is Silobreaker, which aggregates online news and displays it graphically to give a better overview, calling it “insight as a service”. The company is managed by a ten-person staff in Stockholm and London. It is privately funded and is going to seek outside investors this year.

Dothomes is another. It describes itself as the “Google of real estate”, since it lets users search more than a thousand real estate websites from one place, featuring a special “I’m feeling wealthy” search button similar to Google’s “I’m feeling lucky”. The idea garnered several prizes in Europe last year, including Business Week’s award for Europe’s Young Entrepreneur of the Year. The company is backed by three of Europe’s leading early-stage venture capital groups, The Accelerator Group (TAG), Arts Alliance and Samos Investments.

Online document sharing provider Huddle received $4 million funding from UK-based Eden Ventures last year (our coverage). It plans to launch a new round of funding during its visit here next week. Huddle also plans to open a sales office in California at the end of 2008.

Others in the twenty include: Coull, Edocr, Exabre, Groupspaces, Hubdub, Kviqq, Mydeo, Rummble, ShortFuze, Skimbit, Slicethepie, Tioti, Trampoline Systems, TrustedPlaces, Zebtab and Zogix.

The 20 start-ups will pitch their technologies at an event hosted by the Heller Ehrman law firm on Tuesday April 22 in Menlo Park, with a number of Silicon Valley based venture capitalists present.

Oliver Barrett, an entrepreneur and investor from London, initiated Web Mission 2008. He is a cofounder of language learning site friendsabroad.com, where about half a million people regularly practice foreign languages. He also helped launching Make Your Mark with a Tenner, a British competition to promote entreprenurship among young people. He thinks the interaction between the UK and US start-up communities can work both ways. “We might also be able to help some US companies enter Europe”, he said.

The TV-show Dragon’s Den originated in Japan and now airs in a number of countries, including the UK, Israel, Finland and New Zealand. Earlier this year, TV producer Mark Burnett signed a deal with format holder Sony to produce an American version of the show. The US version will be called The Shark Tank. Burnett is currently negotiating with different networks to run it.