Just wondering if its possible to use 2 usb's at once...

...one would be for apps and stuff, the other would have all my music, videos and what not on it? Is this possible?

You COULD have both USBs connected at the same time, but HBC will only read the one closest to the edge first. It'll read the second USB only until you disconnect the first one. As fas as I know, it won't read both at the same time. So you're better off just all your apps and stuff inside only one device at a time.

If you're using an HDD, you could always give a 4GB partition for your apps, and the rest for your other stuff. That's how I'm managing things, and it works great.

I don't know if it will change anything but here is what I've observer
I have launched Monster Hunter Tri from closer USB, it's all fine, we played with friends by online method and I've found OSK (OnScreenKeyboard) to be little uncomfortable for long-range typing, so I've tried connecting USB Keyboard...and it worked o_O
Same goes for Opera but this one was started from Wii as Channel :P
Same goes for DosBox port (just don't remember which one because there are two)

In clean theory it is possible I guess

First of all, NO TALK ABOUT BACKUP LOADERS. NO EXCEPTION.

Second of all, what he asked regarded connecting 2 massive storage USB devices, not a keyboard and a separate USB device. As a matter of fact, connecting a keyboard and a HDD do work side by side, but not two HDDs or flash drives.