Granted, electricity prices are different in different areas, but has anyone done any rough math on the expectation of getting a block awarded?
Sounds like you are asking two different questions:
1. What is profitability of mining? -> Bitcoinx.com has charts how much you can make per day with 100Mh/s. -> http://bitcoinx.com/charts/
2. What is the likelyhood of finding a block? -> Here is a calculator to see statistics around how long it will take you to find a block -> http://www.alloscomp.com/bitcoin/old_calculator.php