This article written by Rich Schwerin appeared in Oracle Magazine in November/December 2004 issue.
http://www.oracle.com/technology/oramag/oracle/04-nov/o64industry.html
This article provides good general overview of BPEL. This article is definitely good for beginners.
For those who are interested in learning about BPEL4WS in details, should go below link
IBM BPEL4WS Tutorial