OskiCat lists books, journal titles (but not individual articles), videos, and other materials in the UC Berkeley libraries. You can also log into "My OskiCat" to renew or request items. You can now send book locations and call numbers directly to your cell phone [here's how].
Melvyl covers all the UC campus libraries, and shows which libraries worldwide have an item. It also lists some journal articles.
For more information, see our Guide to Library Catalogs.