I have a USB device I want to use purely for malware removal from infected systems. However, obviously I am worried about infections jumping from one computer to another, or to my machine when I need to update them. I did a google search, but I was unable to find a free program that meets my needs. The ones I did see supposedly locked the device on the computer the app was installed on, but not on all PC's
help?

I agree, TrueCrypt is going to be your best bet in a free solution.

Here's another great solution i had not thought of

http://isc.sans.edu/diary/Read+only+USB+stick+trick/10588

Use the write protect switch on SD cards (+usb sd reader)

I like the SD idea. I have a portable media reader, so even if the PC doesnt have a reader, im GTG. I have a 1GB card that should do the trick.

You're not wiping it to prevent forensic recovery though; you're just restoring the previous file system to prevent the auto-execution of something like switchblade or some other malware that may get on the drive during use on an untrusted system.