This is just amazing. I love this. I plan to use USUS all the time now.
So I googled it and discovered what it really is: it's how the Russian word дневник, dnevnik 'diary', comes out if you're typing on a QWERTY keyboard with the keystrokes you would use on a Cyrillic keyboard. There's a Wiktionary entry about it; and I didn't even know such a category of -- of what? I guess I'll call it slang -- existed.
So on my LJ, I asked if there were any other examples, and it generated some interesting discussion. One person told me about usus for гыгы (gygy 'laughter' -- think hee-hee); someone remarked that the "usus" of usus is fun in itself. Another example is ghbdtn, which is привет, privet 'hi' or 'greetings', common in instant messaging, with ICQ, Google Talk, etc.
One common example goes in the other direction: Russians typing in Cyrillic often use З.Ы. for P.S. so as not to have to switch out of the Russian keyboard. And one person told me they even sometimes use Ж-) instead of : -) for the same reason!