I've been seeing these everywhere. The no-straps design is totally impractical, but the minimalist in me likes the idea of nothing more than a pure rectangle, maybe in a really bright color.
Clare Vivier's flat clutch comes in several colors and pebble or smooth finish; I like the slightly chunky zipper.
Her foldover clutch looks great in navy with red piping:
Or you could go cheaper at the mall. American Apparel's medium pouch is probably not as nicely made—but it's less than half the price and comes in more than 20 colors:
Zara calls this a wallet. I don't know about you, but I sure don't carry that much cash around. I'm not sure about this mustard color, but you can get in black too: