First off, excellent resource! Now I don't have to jump around books to find all the useful cheap items anymore.
Some somewhat useful items from the Forgotten Realms Campaign Setting (p. 95-97):
Cassil and Nararoot (1 gp [Male], 2 sp [Female]) - Hey, contraceptives are potentially quite useful, depending on your campaign.
Besides, they're really quite cheap.
Disappearing Ink (5 gp) - Potential utility uses.
Potion Belt (1 gp) - Retrieve a potion as a free action 1/round. The 1 gp version gives you 6 slots, while the 60 gp version gives you 10 slots. (Just build it into your existing belt.
)
Stuff from other books:
Blessed Bandage (10 gp) [MIC] - Automagically stabilises target. Pretty cheap life-saving item.
Caltrops (1 gp) [SRD] - Cheap battlefield control possibilities.
Jumping Caltrops (250 gp) [MIC] - See above, except these actually seek out an enemy.