If you've been wanting to explore BPEL, Grand Central Communications has added BPEL support to their network and put together a collection of resources on their developer site. The site include some sample scripts. You can sign up for developer accounts at Grand Central for free, so you should be able to learn about BPEL without buying or installing any software---a pretty good deal.

Also, Doug Kaye points to a BPEL tour by Paul Brown that is worth spending 10 minutes on.