I use pixresizer (or maybe it's pixsizer, I forget exactly). It's icon looks like a greyscale Union Jack.
Loads near instantly and ALL it's good for is resizing pics and some of the basic photoediting things that the camera itself can do.
Consider giving RealWorld Photos ( RealWorld Photos - simple yet powerful image editor ) a try. It is a new thing and still in beta, but it has exactly the features you need. Configurable resizing (by percentage, width, height, longest edge or you can write your own custom resizing in JavaScript) also works in batch mode. Cropping can be restricted by aspect and the program supports lossless JPEG ops.