Hmm...loading wiiware from USB/SD isn't exactly any program...it requires basically an emulator that acts as the wii's hard drive (the nand). As such, compatibility isn't all that guaranteed. Quite a few games run, but don't expect just any game to automatically work.
-triiforce is the most commonly known one. However, as this relies on waninkoko's cIOS, this means that you need to make sure the versions match. rev17 is currently the best choice to play wiiware. It can be used to play wiiware from either SD, USB or the NAND itself (for SD and USB, you'll need to have a nand dump in the root)
-triiforce mrc is a mod of triiforce that adds a decent GUI to it. I recommend this one over triiforce, but that's a personal choice
-from what I hear, sneek has the best compatibility (thus far I haven't heard anyone mentioning something doesn't work on it). And no wonder, as this is a project to run your entire wii from SD. That it can run wiiware is pretty much a convenient extra. The disadvantages are that it can only run it from SD, and that it's (IMO) pretty hard to actually get it working (
link to a guide...but don't ask me anything further).
-just recently, Hermes's USB loader (uloader) gained the feature to load wiiware. You'll need his latest CIOS for it and at least uloader 4.8A (at the moment, 4.9A is the latest version), but other than that, the installation is easier than the previous ones (read: you don't have to mess that much with the nand dump).
This link'll get you started.
I hear quite a few good things about its capacities, but I can't share in it (I dunno what I'm doing wrong, but I manage to crash it everytime).
EDIT: I must've been wrong: it does work on USB. Oh...and uloader isn't exactly the nicest-looking loader out there.
@MrFrem82:
check this page for the info.