I can handle the memory usage, I've tryed uTorrent and ABC opposed to Azureus.
uTorrent just plain doesn't work for me which is odd, but I can live with it (if you define working as getting 100bps on a torrent with 100+seeds and 700+peers then it works, but something tells me it's not liking the way my pc/network is set up), I just dun use it (if you do though and it works, great for ya).
ABC on the other hand worked for a while until I couldn't get it to connect at all. At. All. Not so bad until you find out that your network is infact NOT broken, and nothing's being blocked (irony, nothing was being SENT from ABC either, so something somewhere got seriously broken).
I can live with the memory hogging of Azureus though, I don't normally torrent while doing anything else (cept when playing painkiller or ut2004, but those don't seem to rely on memory as much as anything else).
To be quite frank though, there is no 1 best bittorrent client, just like theres no 1 best first person shooter, no 1 best rpg (you might find several final fantasy players torn between which one in the series they like), and no 1 best zombie slasher fest (dead rising, painkiller...). It's really just a matter of hunting around, finding a list of 5 or more, grabbing them all, and trying them out to find out which one you like most.
Personally, Azureus. For one of my friends, uTorrent. For another the official client (I somehow doubt he'd stick with it if he actually tryed other ones, but to each his own). All I care about really? Does it download data. Does it send data. And does it do that properly (nothing worse than a client that breaks the protocol and sends bad data, besides a user who knowingly misnames a torrent). I could care less if you're on uTorrent, ABC, Bitlord, or even BitComet, so long as you're sending me the data I'm looking for.
As for websites that have torrents to download...Eh, I dunno if I wanna show off my sources. Something tells me you'll either find them yourself given time, or I'll get warned/banned for sharing sites that are very heavy in illegal materials (Copyright violation? What's that?). I like x10 too much to get banned from it XD