[aethertap]

I'm not a photo power user like you are by any means, but I've been using darktable[1] quite a bit lately and I've gotten to where I like it. Here's the blurb from their front page:

"darktable is an open source photography workflow application and RAW developer. A virtual lighttable and darkroom for photographers. It manages your digital negatives in a database, lets you view them through a zoomable lighttable and enables you to develop raw images and enhance them."

1. http://www.darktable.org/

[JBReefer]

Darktable isn't half as useful as Picasa for photo management, and the UI is awful. It does have some nice editing features, but it's a very different product.