The Yn-565 Balto suggests is ok. It's not between the 430 and 580ex though, it's an exact copy of the 580 ex II. It has master and slave functions and can use ETTL, it's just a little less powerful. Same design too. I've heard some problems with this flash though, about it being not up to par with other YN products (eg. breaks and quality control not so good)
Personally, I'd get the Yn-460 II or yn-560 if I were you. They're about the same flash, about same output power @35mm, but the YN-560 can zoom (which is a nice feature!) and has a PC-synch cord input, which is also nice. The Yn-460 is about 45$ shipped.
I got the YN-560 and it's a VERY sturdy, nice, simple, good working flash. It's fully manual, so no ETTL (which is for noobs anyway).
I can recommend the flash. Only 60$ shipped from China. I'd get it over the Yn-460 for the zoom feature alone.
As for triggers: RF-603 (also a Yongnuo product). I got mine in recently and they're fabulous. Similar like the older RF-602 (beware, these are NOT compatible!), but they work as both transmitters AND receivers and you can also put a flash on top of the hotshoe of the RF-603 that sits on top of your camera. Means they're much more versatile.
I have never used Pocket wizards, cactus' or the like, but I really don't think it's worth it whipping out a shitload of money for that if there's an option like this available that's cheap, simple and works. The RF-603 run 30$ a pair.
Now I don't know exactly how this all works, but the T3i has an INTERNAL transmitter that (I think, not sure) works as a transmitter too. I'm not sure if this would also work with Yongnuo flashes, but you might want to do
a little research on this. Check out Photography-on-the.net/forum, you'll find info there and otherwise you can always ask in a topic.
I can imagine the internal transmitter doesn't work as well as dedicated triggers though.