Just depends on what you want. If you are using Tiger (OS X 10.4), then I'd recommend AdiumX rather than iChat. If you are on Leopard (10.5), then I'd say just stick to iChat unless you want to be able to use other messenger protocols such as MSN, Yahoo, and more.
I'd probably recommend an RSS reader for all those sites you like to read from. I use NewsFire which is shareware, but Vienna is a great, free alternative.
For FTP, I use Transmit. Also shareware, but Cyberduck is also a free and great alternative.
For Torrents, go with Transmission. I don't bit torrent much, but I've heard it's one of the best apps out there on OS X.
Again, there are so many greats apps out there. You just need to know what you want. So anytime you are looking for an app, just check versiontracker.com or macupdate.com. Those are some of the best sites to find apps you are looking for. Also osx.iusethis.com is a good site to find out what apps are "hot." And if those fail, try either Google or just post a thread here for additional help.