LUbuntu - it's a lightweight version - I use it at work inside VMWare with an Internet USB Stick - only to browse the Internet, because the company blocks facebook, yahoo mail, google mail, and so on
One solution would be to root your phone (no need to install a custom ROM), then install Titanium Backup. From Titanium Backup you can uninstall built-in system apps completely, like Facebook or News and Weather (that's what I uninstalled).