I've got an Excel Spreadsheet that I created for our League. It does handicaps at 90% of amount over par but could be easily modified to use whatever percentage was desired.
We run our League at two different courses (12 weeks at each - April thru October) and I keep separate stats for each park. Basically there are Tabs along the bottom for different information, the two most important tabs are "Raw Scores" (where scores are entered) and the "Summary" sheet which shows each player, number of leagues attended, raw average score, handicap, and points accumulated. Players get 1 point for each week they play and an additional point for each player that they beat (after handicap adjustment) each week. New players play for free their first week to allow them to set a handicap. E-Mail me if interested : email@example.com.