If you connect it to the same computer it is "paired" to for syncs, you can force the pass code off:
-Connect your iPod Touch to iTunes
-Press or Hold the power and home keys 10 seconds.
-Screen goes black, now release the power button
-Make sure you do not release the Home key until your iTunes says "We have detected an itouch in recovery mode."
-restore the ipod
You will, of course lose any content which has not synced back to itunes from the ipod...
see also http://support.apple.com/kb/HT1212