You could always continue with your collecting hobby, and do another on the side.
I'm not sure what you are capable of doing, but here are a few suggestions.
Gardening - if you don't have a large enough yard, or a yard at all, you could try a small box of plants or one of those Japanese bonsai trees
Crafts - Collages are sometimes rather fun, cutting up hundreds of magazines to create one piece of art
Cooking - Serious cooking, not just simple meals and whatnot, also a useful skill to impress dates.
Crochet/Cross-Stitch - I dunno, might be fun lol
Learn an Instrument - Challenging, possibly fun, guitars/pianos/violins and so on.