That Wal-Mart CF replacement for IC screw-on bulbs is almost $6 here!
A friend suggested to look for the 18" flourescent bulb (and holder) in the lighting section of Wal-Mart.
The 18" "aquarium and plant" bulb was $5, and the holder was $9.
So, two CF replacements for my current 10G hood would be $11.
New 18" + holder which fits the 10G nicely would be $14.
I think the 18" puts out more light, so if you're willing to spend a little more money, the 18" + holder is a good deal for a 10G.
BTW, the 18" holder already has a regular (cool white?) bulb in it, so if you don't need the special plant / aquarium bulb, you're down to $9.