last.fm the 'social radio' pioneer announced a new round of investment today from business angels and Index Ventures:

"Fast-growing music site Last.fm has taken its first round of institutional funding from Index Ventures, an early backer of Web-calling company Skype and U.K. betting exchange Betfair, the company said on Monday.

The London-based site has exploded in popularity since last August when it launched a new method of music discovery that recommends songs by tracking a listener's song-playing habits and automatically mapping them to fans with similar tastes.

Index was joined in the latest round by Last.fm's first-round of angel investors Japanese blog backer Joi Ito, LinkedIn.com Chief Executive Reid Hoffman from Silicon Valley, and German blog company founder Stefan Glaenzer."

Congratulations!

Last.fm is around for 4 years now and is a big role model for me on how you can bootstrap a company successfully and believe into something. Here is there initial homepage. The founders rented an apartment in London, got the software to work and hitchhiked on free sever capacity at that time.

The I met one of the founders in 2003 in Hamburg and the angel network I was part of, was seriously considering an investment but could finally not agree on one. Last.fm still has a 'revenue challenge' as sales from mp3s and ads are only trickling in. But last.fm was stubborn enough to stay on the path and develop 'social radio'. Fantastic job!

Another interesting thing I found lately is that my music player at home called Amarok that nicely sorts your mp3 collection also build your profile in last.fm automatically whenever you tune into something. So last.fm can make useful suggestion to me whenever I tune in there.