One of the easiest methods for DVD->avi (XviD) would be using Auto Gordian Knot (guide
here).
For DVD->MPEG-2, well, take a look
here, my person preference of the two methods listed there is DVD2SVCD, and while it says that it requires one of two programs which aren't free, the latest versions support QuEnc, a free encoder.
I dunno about .wmv conversion I don't use that very much