This is the way I store my framelits/thinlits. Those that have a matching stamp set are in the CD/stamp case with the set, and those that are stand alone framelits are stored on both sides of the case. I cut the information/label sheet down just a bit on each side and tuck it into the outer plastic sleeve of the case. I label the "spine" of the case as books are labeled with the kind of framelit it is to allow me to find it quickly in storage.
The magnetic sheets I use are from Hobby Lobby. It comes in a pack of several sizes for $2.99. (Some are larger sheets than I've shown here.) There are other magnets such as magnetic vent covers at home improvement stores that some use with ease, but I like these best.