I have Premiere for the complicated stuff, but I more often use VirtualDub (freeware) and JASC Animation Shop for the simpler tasks.

VirtualDub can piece together .avi files. Animation Shop can reverse a video. And both applications can compress a video using whatever codecs you have installed.

VirtualDub will assemble a video from image sequences, as long as they're in BMP or TGA format. Animation Shop, on the other hand, will work with almost every image format exportable from Poser.

If you want to convert your AVI videos to MPEG format, I highly recommend TMPGEnc, a freeware encoder.