I had searched the internet for info about the Droid X supporting USB OTG and only found out that the OG Droid could do it. I took a risk and bought a micro USB to USB OTG cable and:
It did absolutely nothing, both with a mouse and a flashdrive. So I just wanted to let others know that at the moment it does not appear to work. (Could be a ROM or driver thing, I am on Liberty GB 0.9 but I don't think so.) However if anyone has any tips or ideas to make this work, feel free to tell me.
EDIT: I tried leukram's idea and still had no luck. I tried rebooting the phone with just the cable plugged in and rebooting the phone with the flashdrive plugged into the cable. Both methods did nothing. Also I did change ROM's but I really think that the Droid X simply doesn't have the ability to do USB OTG.