I use MAC Mineralize Foundation Loose Powder over my my liquid foundation. I like it a lot and it works well with my oily skin. I'm medium and warm toned, but have a friend who uses the same product in a much lighter shade and she's cool toned, and has dry skin, and she loves it too. It's impressive how well it works for both of us!

I use bare escentials and love it! i swear it helps clear up acne when i use it too!

The only mineral foundation that I've tried and will probably not try another brand is from Mary Kay. You get double the amount that Bare Minerals offers and it's cheaper. What I really like about this foundation is that it mattifies my skin but looks flawless, not shiny (since I have oily skin). The coverage is buildable and can be used to set liquid foundation. And it can double up as a concealer too!

Mineral powders are very hit or miss. The hardest part is finding one that is a good shade match. I highly recommend bare minerals. I think they are by far the best on the market. Also, if you have oily skin be sure to use a primer, but minerals are also a good choice because they help keep oil under control.