You could always let your spare bitcoin sit in your wallet and never touch it and let it increase from btc value rising.
You could also put money aside over time and dedicate a certain amount to something you could use or blow it on and not care.
Then gamble that little spare bit on a site like PrimeDice or something. 1 big bet. If you lose it, no biggie. If you win, that's double.
Or you could always find a popular market of things you could buy & sell for profit. Like gaming related or something.