I'd recommend to follow up on my questions in
https://bitcointalk.org/index.php?topic=77650.0 - It's really uncanny, as I planned to do something similar ("bitdust" was even a ticker symbol I considered) as soon as the dividend API would be released. Before that it wouldn't really make sense and I hate poor and/or rushed execution...
Anyways, you can calculate for each second since the blockchain started how many BTC 1 MH/s (or 1 KH/s) would have generated... then just sum up accordingly for hours or days and pay as dividend. All you need is either a running bitcoind + asking for the block headers via RPC or running bitcoind + armory and having it already nicely packaged. Libbitcoin might also work, I haven't tried that one yet.
If I only read "some day I'll do the work to pay out correctly" I start looking like this -->
Even if it's tiny amounts of money, you're still resposible for it and should put in some effort (it's not even hard, my scripts were finished in under 2 hours) instead of looking for a quick payment.
