I personally wouldn't buy a non-intel machine unless the price was right or you want something with classic support. Intel is the present and future for what seems to be a long time. I wouldn't, however, recommend a core duo MacBook or MacBook Pro, as both of the first generations which were core duos had numerous problems with overheating, and the MacBook Pro's X1600 that came with it is underclocked. Besides, core duo only supports up to 2 GBs of RAM which is okay for now, but in the future it won't be, especially if you are going to be running virtual machines.
Either get a G4/G5 at the right price ($400 or lower) laptop, or get an early core 2 duo MacBook Pro or MacBook if you are worried about price. If you need a cheap computer with an average graphics card and is intel, the White MacBook is great for only 949 dollars with the education discount, heck, it is better then the AluBooks in some regards. Or, if you do some shopping, you can find the previous Penryn MacBook Pros for around $1200, which is the best bang-for-buck ratio of any Mac laptop out there. It all depends on your needs.