Sites themselves have nothing to do with the torrent speed. That is the main advantage of torrent downloading, over direct downloading. The sites server is not handling your download at all. Torrent speed is solely dependent on the following:
1) Seeder / Leecher ratio. The more people that have the file, the faster it will be distributed.
2) Whether or not the current people that have the file have their upload capped. When you cap your upload, you are severely effecting the speed of other users. This is especially true with low seeder torrents.
3) How many trackers the uploader of the torrent added when she/he added to the site. If a torrent is using multiple trackers for different sites, the uploader is responsible for correctly adding them all, so that all of the trackers for this torrent are being utilized.
4) Number of torrents YOU are downloading. While this may seem obvious, the more torrents you download, the slower they all become. 1 Torrent as it is, can really squeeze the limits of a routers NAT. 2 can cause a bottleneck, slowing them both down.
5) Port forwarding correctly. If you do not have your port forwarding done correctly, this could effect how many connections you receive when the tracker updates your client.
6) Global MAX connections not set properly. By having a global MAX connections set to high, you can overload your routers NAT, forcing you to restart you router, modem or both. By keep it too low, you can be giving up bandwidth that your router can actually handle. Play with this number. Rise until your router starts losing its connection, then drop one notch.
a good torrent site would be thepiratebay.org it apparently offers fast downloads and there are comments for each torrent so you know if its safe from others which have downloaded it. =]