Points.com is legit. I think they provide management services directly to many of the loyalty programs.
Points.com also provides transfer of points from one program to another, but the transfers can be highly unfavorable. For example, If you can trade 1000 MyAir miles for 500 GreatHotels points, and 500 GreatHotels points for 250 FreeAir, Points.com will offer to transfer 1000 MyAir to get 250 FreeAir. There can also be transfer fees. It's usually only a good option if you need a very small number of points to top off an award.
However...
One good way to extend your points is to go to the Aeroplan shopping portal and buy something. Like a song on iTunes. All you need to keep your miles alive is one point added or deducted. So if you buy a $1 song on iTunes and you are logged into the Aeroplan shopping portal (I forget its name), you'll get one point, and your miles will stay alive another year.