I'll rank them by my preference
2) TuneIn / Streema / Radio / iHeartRadio (Tie)
2) Raditaz (Tie)
4) Grooveshark / Rhapsody (Tie)
6) Vimeo (Videos, but higher bit and sound quality then YouTube and Dailymotion - also a wildly popular site)
7) Audiolizer / Mixpod
8 ) Youtube, Dailymotion, Vevo, Blip.TV and Metacafe (Tie)
9) Pandora / Playlist / iHeartRadio Custom
13) Sony MU and all other products.
14) Spotify / Finetune (hate it).
I like Rdio because the site is clean, high quality, full of content, social friendly and very reliable.
TuneIn, Streema, etc I like my local radio!
I like Raditaz because I can just go on the site and listen, and it has no skip limit and it generally gives me much better results then Pandora. Also the company is more professional, I hope they overtake Pandora. Plus you can do hits by decade, and go all the way to the 1920's or so.
I like theRadio because I like it's a very simple site and it has a good library.
I like Grooveshark and Rhapsody because of their feature, but dislike the overabuse of needing to be a plus or better member.
I like MOG because it's a nice alternative to Rdio.
I like Vimeo because it's a very high quality, professional grade video sharing website.
I like Audiolizer and Mixpod because they use YouTube and Dailymotion to make playlists. Generally decent quality and large large selection. The error is some videos aren't allowed to be viewed off site.
I like video sharing sites because of selection - YouTube and Dailymotion are immense sites that have Vevo and many sponsers posting. The others generally are useless because of their targeted audiences (BlipTV targets webshows and original videos, and Metacafe targets viral videos and media).
Pandora and Playlist, both sites that generally work and don't work. Pandora has a skip limit and gives me entirely mainstream and somewhat unrelated artists that I hear too often!
We7 has an incredible site and engine, but it is often irrelevent.
Slacker is hard to use and slow to get stared on, but great otherwise. Rarely use it so it's ranked low.
Bluebeat ... Not much to say here. Generally fails.
Last.fm - how do I even use this thing?
Sony MU - I wouldn't pay for online services when Rdio is free and has a larger selection
Spotify - P2P, requires facebook, bad selection, quality is declining and a desktop program.
Finetune - a radio program with only 30 second previews? Wow.