My wardrobe is mostly made up of T shirts. I like to wear cute camis underneath to spice them up some, and right now Im shopping online for some but I can't really find any that I want. What I'm looking for are ones that don't have any kind of detail, like ruffles or lace (except at the bottom) or ribbed because it looks weird under a shirt, and I want them to be thin so i don't look too bulky and also kinda long, like longer than a normal T shirt. Anyone know a good store's site where I can find some like this?

Try Aero.

yeah..aeropostale..or american eagle.
charlotte russe has cutes ones sometimes.

Aeropostale has a lot of camis, but most are ribbed...
Rue 21 has a lot of tank tops like the ones you want.
They don't sell online. You'll have to go to the store to buy them. They are pretty cheap. $10 each.