Are you looking for OEM or aftermarket?
For oil filters, http://www.trdsparks.com
sells 10-packs of the Toyota filter for $35, it's one of the best for our xB's. Don't bother with the TRD filter, just the regular black Toyota one. Same for coolant if needed, though the Toyota long life is 90,000 miles I think so you should be good other than topping off. For oil, switch to synthetic. I'm currently using Mobil1 but have heard Penzoil is the best for our cars. Use 5W30.
Trans. shouldn't need a flush unless you were towing, loading the box down a lot or it's shifting rough. if you do decide to do it, professional flushes can be $$ because they cycle through 4-5 times the ammount of fluid the trans actually holds, but gets it clean. Toyota uses a synthetic type T-IV. For aftermarket, Amsoil universal ATF says it meets the Toyota spec, as does Redline Synthetic D4 ATF and Synthetic High-Temp ATF, don't use any other Redline ATF.
Brakes and pads, I usually go to autozone and buy the generic Duralast gold pads and Duralast rotors. it isn't worth it to get the rotors balanced, new front rotors are $54. Drums I no longer touch, but they should last a bit longer than the front pads.
For engine tune, NGK copper plugs work fine, or get the platinum if you want to change them less often. You won't get a performance increase with them though. For air filters, I think K&N makes one, as does TRD that fits the stock airbox. The xB doesn't come with a cabin air filter, you can make one by buying one of the trim to fit ones from Walmart and put it in the tray behind the glovebox.
that's pretty much it other than checking the tires and other fluid levels (brake, power steering, washer) and maybe throw on a battery charger.