Issy had just started walking at that age, so we walked in the backyard alot! Even if there crawling the tactile feel of grass or bark is excellent for them.
We also went to active movement at the library .. (on a side note you can get an active movement dvd from sparc for free).
Mainly music is usually cheap.
We also did jumping beans and swimming
Oh and we still rotate her toys .. once a week I set up her area with all "new" things (oh and things like big boxes for them to crawl through are a hit.