Well, I’d bring back mine to life if some bastard who I lent mine to 9 years ago would give it back (its probably a burnt out door stop now 🙁 ) Slashdot.org is running a story on an ethernet adapter for the old personal computer. It apparently hooks into the expansion port of a Retro Replay card. The operation system Contiki has support for the card. Contiki featues a TCP/IP stack, a web server, a web browser, a VNC client and a GUI. Have a look here for a screenshot of this in action.
Apparently it’s not the only option for networking your C64 either. There is also The Final Ethernet as well. It looks like its more of a DIY job though, with no plans to put it into production. Also, if you’re still wanting to upgrade your C64, CMDRKey.com offer hard drives, CPU accelerators and RAM drives.