For many people new music is an addiction. It starts when you're young, a friend's older brother hands you a Fugazi tape and all the sudden you're hooked, spending all your hard earned cash at the record store.

But the search for new music is easier and cheaper than ever. With internet radio and social music sites, there's now a whole realm of friends older brothers just a click away.

A while back I tested out iLike for the Monkey Bites blog and I'm hooked. ILike is a actually a whole social networking site, but I haven't been back since I downloaded the iLike iTunes plugin. I always wanted to know what my friend's older brother was listening to, but I never really wanted to spend time with him.

What makes iLike great for finding new music is its integration with iTunes. ILike adds a sidebar to iTunes and provides music recommendations based on what you’re listening to at the time. The sidebar also syncs to and updates your iLife profile so others can see your listening tastes.

There are two categories of recommendations from the iLike sidebar: established artists and new, unsigned artists. When you’re listening to a song and you see an iLike recommendation you like, just click the arrow beside the name and iLike pauses your iTunes playback and streams the new song from its host site. For the established artists you get a 30 second sample and link to buy the song (from the iTunes Music Store).

Music for unsigned artists comes from iLike’s partner site, GarageBand, and you can listen to the whole song. If you decide you like the song there’s a link that will open your web browser and download the file. It would be nice if iLike could somehow just download the song in the background and automatically add it to your library, but that currently isn’t possible. It would also be nice if iLike supported other music players and the company claims to be working on that, but for the time being if you aren't an iTunes user, iLife probably isn't for you.

Last.fm is another popular site that's been helping me discover new music. Last.fm is essentially a web-based, user-generated radio station. Like iLike, Last.fm offers a downloadable program that integrates with iTunes and other popular services. 

Last.fm's software doesn't directly attach itself to iTunes, it runs as a standalone program that streams music from Last.fm. Last.fm's software parses your iTunes library and tracks what you've been listening to so it can display the information on your public page. Last.fm refers to this process as "audio scrobbling." 

There is an older, unsupported plugin that does integrate with iTunes, but I haven't tried it. Last.fm also has another program available that can track what you're playing on your iPod if you use that more than your computer.

If downloading additional software isn't your bag, Last.fm recently added a Flash-based music player which lets you listen to music streams in your browser window.

There are a number of other sites out there as well. I've had good luck with Pandora, a fairly new service from the creators of the Music Genome Project. Pandora is dead simple to use, just type in a band you like and Pandora will build and begin streaming a playlist of music similar to the band or artist you entered.

Pandora is limited to your browser window, but offers some nice features like the ability to bookmarks songs and artists and an explanation of why it thinks you will like the song it has picked. You can also email your stations to friends. Pandora recently added a new search feature called backstage that lets you search fro more information the artists you've discovers. The search results include bios, discography and further recommendations.

Qloud is another popular site, though I've had less luck with it, the javascript-heavy interface may turn some users off. There are some nice features like search auto-complete and live search results, but these fancy features come at the expense of your back button. Qloud requires Windows Media Player for the samples it offers.

As for the recommendations, well they vary somewhat. To test each service I searched for bands similar to Neutral Milk Hotel, Talib Kweli and Justin Timberlake. In all three cases none of the sites suggested the same music though they did often overlap on one or two songs or artists. Oddly the results for Neutral Milk Hotel, which is arguably the most obscure of the three, were almost universally better. In my experience the more mainstream an artist is, the less precise your results are likely to be.

For my own tastes, Pandora returned to best similar artist and also managed to pull in an interesting selection of similar, but different results.

I can't really say any of these sites is necessarily better than the other, they all work slightly differently and for the true music nut, one will never be enough.