I will be there in a few weeks when the ice melts and I've been to algonquin about 30+ times in the last 5 years.
A nice trip (not too hard but still requires some work) is the 80km Canoe lake loop. If you toss me an email I can give you far more info than you need.
Buy one of these for the location you are going:
http://www.algonquinmap.com/ because the official park map will kill you.
Pic related. Took this last July.