Trying to browse my way to OGNL reference, a sad greeting awaited on the OpenSymphony page. Apparently it has been decided to put OpenSymphony to rest.
Many of the projects such as Sitemesh, XWork/WebWork and Compass continue their happy lives elsewhere.
For all the rest the official recommendation is to use the Wayback Machine.
A couple of direct links regarding OGNL for your convenience: