VW Transporter vans are the most popular small van to use in a campervan conversion. Since being the first vehicle used in popular camper van conversions, VW have slowly improved the original vehicle to get to the current T5 incarnation.
VW Transporters are smaller than most vans, but are built more like cars (think VW Golf) which make them hardy, easy to drive and good on fuel.
Perfect for everyday use campervans, or weekend camper vans.
eBay is a great place to find lots of Transporters. This is one of the few places you can find a bargain Transporter.