Under Windows a simple Addon exists with wich I can sync my funambol events and contacts with Thunderbird and Lightning. I couldn't find such a tool for Ubuntu yet but it would be very helpful for me.
AFAIK, there are only "inofficial" builds of the Funambol add-on for thunderbird. Take a look at memotoo.com's site, there are build for Windows, Linux 32/64 bit and even OS/X. The site is in german, but you can set the language to english using the controls at the very top of the page.
I'm using those add-ons with lucid, oneiric and with Win7 - works like a charm!