I'm just going to be saying what others have said here :P
Dreamscarred Press is simply great. They're the devils that got me hooked on 3rd party publishing (and eventually making it myself). Their stuff is interesting, fun, flavorful, and balanced. I recommend Ultimate Psionics!
From there on out, there are a lot of good options. Interjection Games makes unique classes and has a wonderful Truenamer. Raging Swan has amazing GM tools/advice. Frog God has awesome monsters. Legendary Games is the go-to for 3pp mythic. Oh! And Drop Dead Studios' Spheres of Power is fantastic! Kobold Press is quite popular and makes very pretty books (I've got some gripes with editing and the balance of spells/player options in Deep Magic, but there are plenty in there that it isn't the end of the world if you ban a couple.)
Check out http://www.endzeitgeist.com if you want to know what to get and what to avoid!
It's hard to go wrong with anything on bookrat's list on the first page.