I garden too. You can even buy seed packets in late winter for .10 a pack or buy them @ end of season sales the previous years for a fraction of what they sold for @ the beginning of the season
You can also harvest & store the seeds from the plants you do have.
rummage sales <-- I don't know if you'd want to call it a hobby but it's fun because you'll never know what you'll find & it's cheaper the going to the thrift stores. But with the gas costs lately it's only with going within a short range
playing computer games
surfing the net for freebies & coupons