Rainmaker Systems Inc., a provider of business e-commerce technology, said Chuck Geiger, a former PayPal Inc. chief technology officer, has joined its board.

Geiger, who is currently CTO of Chegg, a textbook rental company, has also been CTO of Ask.com and Wine.com. Geiger was also vice president of product development for eBay Inc., which owns PayPal.

"Chuck brings a strong technical background and significant e-commerce experience and expertise to our board, and he will be a valuable asset," Michael Stilton, Rainmaker's chief executive, said in a press release June 16. Rainmaker is based in Campbell, Calif.