-Go here:

http://209.122.88.33/ArticleSearch/visitsearch.htm

Search with keyword workbench should give you several free plans, a clickable workbench page (you can order the fellows blueprints) and probably some discussions on the subject.

-Start here:

http://www.utdallas.edu/~rick/

Scott Landis' _The Workbench Book_ is considered a landmark survey of benches; it includes plans for several. Not free though.