Other options!
I forget what book had this extra skill usage, probably C.Adventurer. Basically, you can make a balance check at a -10 penalty to resist being tripped, instead of a str/dex check (stability and 4 legs bonuses still apply). Which for most is a bad deal. But if you max ranks in balance, you can eventually be very hard to trip. If this isn't a printed rule...my DM made it up an I adopted it myself.
Prone Fighting (is the name,
iirc) from Complete Warrior is a feat that actually makes you fight better prone than standing! (because it removes all the penalties and lets you retain the ranged AC bonus) I think it also lets you get up as a free action w/o AoO, not sure. The only downside is that it requires Lightning Reflexes, which
IMHO is one of the most useless feats in the game...
All of the options I've listed are mostly for agiel fighters, monks, rogues, etc...Which is as it should be. Burly armored Fighter types should be vulnerable when knocked on their asses, kind of like flipping a turtle on its back.
That said, non melee-ers can often do fine while staying prone. You can fire shuriken and crossbows while prone just fine. Mages can lay out death and destruction just fine from the ground. Especially if they teleport out of melee range. One time, my party fought a dragon that was standing on the ground and a guy tripped it. Its breath weapon worked just fine from prone.

Just pointing that out, too.