Although most people will probably never remove the 8GB microSD card preinstalled in the HTC EVO 4G, those who swap cards often may find it cumbersome to have to connect the phone to a computer to transfer files to and from the card. If you're one of these people, then you might consider picking up SanDisk's diminutive MobileMate Micro.
The tiny USB card reader has been around for a few years, but it's only a couple of bucks on Amazon right now and is such a useful accessory to have on hand not just for the EVO but for any other device you might have that uses microSD cards as well. Just about every Android phone out there comes with a microSD slot, so the MobileMate Micro has long-term value and is really just a nice thing to have in your gear bag.
Sometimes it's more convenient to connect the EVO to a computer and browse the card that way, especially since it's beneath the battery, but there have been times when this little USB reader has come in handy for me. And for just a few bucks, how could you not get one?
I have the black-and-gray version of the MobileMate, but it's also available in black-and-red to perfectly complement the EVO.