- Learn a new language
Sites like duolingo & Memrise offer free courses - Knitting (not just for old women)
Making something from scratch is very rewarding, making something you may wear is even more rewarding. [Video] - Learn to pick a lock
Think of it as a game, not a way of learning to be a criminal. This set will help. - Disc (Frisbee) Golf
You just need a frisbee, a couple of mates and if possible a course (optional) - Geo-Caching – aka GPS treasure hunts.
You basically download an app that gives you clues to locations of hidden ‘treasure’ near you, you then hunt for the treasure container and ideally place something of interest inside. Find out more on Geocaching
- Learn to play games
Play Chess online | Learn to play Chess - Flying aircraft
For around £25 (or here) you can pick up a small agile quadcopter, these things are great and powerful. The problem with this is you may get fixed on the more expensive ones! - Reading
Most of us can gain access to a library for free or on the cheap. Failing that check this awesome way of reading magazines for free.
Also sites like Google Books are also great places to start - Exercise
Don’t automatically think of things like running but look at alternative exercise like Tricking | Yoga | Lounge Exercises | Dance - Continued Learning (think outside the box)
How to tie a knot | Start your own website | Price Anchoring | Freelance your other hobbies | Tons of online courses | Maths