Can't be arsed reading the entire thread, but
www.audioscrobbler.com may be worth a look. Basically it's a plugin you install for (whatever media player, seems to support most), and you register for an account.
As you listen to each song, it sends the details off and builds a musical profile of your taste, and then after you've listened to enough it'll start comparing you to other users and will offer recommendations based on the sort of stuff similar people (People with similar taste, it's a little superficial to say that these people are automatically similar, but I'm sure you get my dritf) are listening to, allocate to you 'musical neighbours' and a bunch of other stuff. You can found groups and manage a friends list and whatever else, but these aren't really where the bulk of the utility from using this stem from (at least so far, I haven't been using it long)
for the purpose of illustration,
http://www.audioscrobbler.com/user/Spl33n/ is my account. Some of the recommendations are a bit whack, but it's more accurate than I expected.
Prior to this I mostly used google
Find a band you like, see who they say they like, investigate other bands that members have been in, bands that are compared to them, and maybe bands they've toured with, etc.
More recently I've also used trial and error, largely thanks to ADSL
Download an album, if it's good, investigate more, if it sucks, delete it and try again (Obviously not as viable on dialup or whatever).