What can I do with the physical copies of my Steam games?
Some people point out that if Steam is ever disbanded, you lose access to all the games you bought from them. If you will still have the physical copies of the games, it wouldn't be an issue. Note that some games require Steam anyway, so with those games the physical media won't help.
If you aren't sentimental about the box, manuals etc., you can throw those away and just keep the DVDs in some designated disk holder - those are very efficiently packed together, I don't really see an issue with space or weight.
If you ever find yourself without Internet access for a prolonged period of time (for instance, if you join a shipping company), single-player games can still be installed from their boxes.
If you trust Steam, have permanent Internet and don't care about your game boxes, then no, there isn't anything good to do with them. If you already have an eBay account you can offer the game boxes there (just don't provide the serial numbers), other than that I wouldn't bother.
If you feel your game will become a classic later on you can hold on to the manuals and sell them again in 15 years for collectors :)
The CDs are useless to anyone else from a software installation perspective. If none of Oak's reasons for keeping them are compelling enough, I suggest you dive into the world of recycled materials craft projects. If you do a search or two on Google, you'll see a multitude of ideas ranging from:
- clock
- coaster
- desk mirror (to see people coming up from behind you or for other mirror-related purposes)
- disco ball
- frisbees
- picture frame
- weights
Let your imagination run wild!