O'Reilly Network Safari Bookshelf is basically all the O'Reilly computer books online. It is a pay service that the library has subscribed to and is open to anyone with a campus IP Address. Check it out at http://safari.oreilly.com/
Off campus access is possible via the library VPN. The access URL is https://vpn.lib.ucdavis.edu:11001/ It does not appear to be possible to use this service off-campus through the library's proxy server.
It should be noted that there are some limitations to the service provided. First, everyone visiting the site from the UC Davis campus is automatically logged into user account "Davis Davis." This means that all UCD users share the same set of bookmarks, recent pages viewed, etc. Second, it seems that there is a (low) limit on the number of concurrent sessions allowed from the UC Davis campus. So if a lot of people are trying to use the Safari Bookshelf at the same time, you will get error messages saying that the number of concurrent sessions allowed from your organization has been exceeded.