Stone of Good Luck (20,000 gp) gives +1 luck on all saves, ability checks, and skill checks.
The Elusive Target tactical feat, in addition to the power attack negating and attack redirecting abilities, also has Cause Over-reach. Any enemies that attempt an AoO provoked by your movement that miss are subject to a trip attempt from you. This attempt is just a free attack, NOT an AoO, and the tactic explicitly says you cannot be tripped if you fail.
The problem is when the DM stops having monsters try to AoO you....
You should also be looking at the entire Setting Sun discipline from Tome of Battle, which gets a ton of throwing techiques that use the trip mechanic. The 9th level maneuver lets you double move and attempt a tripping throw every 10 ft you move, with a ridiculously fast scaling trip bonus based on how far you've moved so far, which also amps up the damage of the throws.
Also, some throwing prestige classes. Namely, Master Thrower lets you make a free trip check using dex mod +4 on *every* thrown weapon attack. The Bloodstorm Blade lets you treat thrown attacks as melee attacks for a round by spending a swift action, which as far as I'm concerned means you can now do thrown trip attempts if you are wielding a tripping weapon (BB gets a separate ability to ricochet back his weapon so he can full attack throw w/ the same melee weapon, so just chuck a guisarme or something).