there are none here, but there are some on the pdga.com and i believe discgolfunited.com was working on one as well.
basically, the easiest way would be to look at tournament results for a given course (or do your best to estimate).
it will take a few rounds of everyone playing to really get a feel for it. you can calculate virtual ratings and use that to develop score handicapping.
basically... to estimate an ssa without previous tournament results...
take every hole that someone who could throw an accurate 500' could realistically deuce (within reason, hitting a 2' wide gap at the 475' mark is not realistic) with a great drive.
multiply the count by 0.6
take every hole that has a reasonably large amount of trouble. that is, if you miss the fairway (target landing zone, ~15' of width), your chances of bogey are 50/50 with your chances of birdie nearly nil.
multiply the count by 0.2
take every hole that is not reachable in 2 perfect 350' drives to get yourself a 50' putt. basically zig zag holes and holes beyond 750' (but below 1100', make sure to compensate for downhill).
estimate on SSA = (# of holes * 3) - (available deuces * 0.6) + (possible bogeys * 0.2) + (number of unreachable 3's)
here is an example breakdown:
available deuces: 1,2,3,4,5,6,7,8,9,11,12,13,14,16,17,18 = 16 (16 * 0.6 = 8.4)
possible bogeys: 2,6,12,15,16 = 5 (5 * 0.2 = 1)
unreachable holes: 0
SSA estimate = 54 - 8.4 + 1 = 46.6 ~= 47
47 = 1000 rated round.
to make it easier just assume that 1 stroke = 10 rating points (in actuality, every stroke on either side of SSA changes the value of a stroke by about 0.3 points, but it's not worth over complicating it).
the hard part is actually getting the data to get handicapping. the easiest way is to work from previous league results or to set up a week or two where every night people can play an "official" round for free and turn in a scorecard. i would say a minimum of 4 rounds are needed to calculate a rating.
once ratings are calculated use ratings to handicap, 10 points = 1 stroke.
once your league is up and running i would suggest updating ratings at least once a month (or every 4 calculated rounds per player) as some players will be rapidly improving. this could be done after every round even once there is sufficient data.