This is easy, but you could potentially break everything with an errant rm -r. You need to grab PTerminal, a command line tool, from the Android marketplace. From there, you navigate to your system/bin folder (where the binaries are kept) and type telnetd to launch the telnet program which lets you login to the phone remotely.

Assuming your Wi-Fi is switched on, you can now type netstat to get your IP address. From there, you just grab a computer on the same network and telnet in. You now have root access to the entire file system. This is the dangerous part, the root user, or superuser, is the God of the computer and can do anything, so proceed with care.