Every midshipmen gets paid $864.30 a month before deductions. Deductions for each month varies depending on whether you have your ACE loan paid off, what state you're from, etc. It also depends on what year you are (Plebes get deducted more money to pay off the loan as compared to 2/C year). Any money left over from the deductions and paycheck is rolled over to a "held pay" account which is released at the end of each semester (we're talking about $800-$1000!)
Plebes see $100 each month in their bank accounts. 3/C get $200, 2/C get $300, and 1/C get whatever is left after deductions (about $500-600 so no held pay). The flat rate for the three underclasses is a good thing as it forces you to budget and you are always guaranteed that money. Plus, you get that giant lump sum at the end of each semester. As a 1/C, you are given everything that is not deducted, but some months, there are lots of deductions so your paycheck goes up and down. One month I made around $700, but a few months later I only got $250.
After leave periods, you will be given money for COMRATS (Commuted Rations) ie. reimbursement for food over leave that is added to your held pay. It's a flat rate by the number of days of leave you had. For Thanksgiving (I think it was 5 days leave), I received $27.80.
No one gets any bonuses for any special jobs or anything.