Thankfully, I've always failed to find any appeal in collecting anything. I even play Magic: the Gathering yet don't bother keeping any but the cards I know I could use.

I would just find any general-purpose media manager (here's a few, but googling "manage your collection" will give you TONS of hits). Almost all are going to have a "comments" or "description" entry which you can use to write your reviews, and you will probably find one or more with a character limit for it.