Please Suggest a weekend electronics project

I am tired of spending my weekends watching serials, movies and playing games and I want a break from work.

I was thinking that a two-day electronics project would be an ideal way to spend the weekend. I have built some robots before (http://www.beamindia.net) and have some fundamental electronics knowledge, soldering skills etc. A robotics project more complicated than the last robot I built (was a long time ago) would be time consuming and I don't want to do a smaller robot either.

So I need something simple enough to be done in 2 days and not a robot. I don't to buy any DIY kits either. Any suggestions? Thanks.