Check out the imagination tree website, playathomemom.com (something like that) plain vanilla mom on Facebook.
See how much season tickets to local activities are - sealife, farm/soft play type places. Try out soft play places - not all as awful as you might think and some are more reasonably priced than others.
Get into messy play at home! See the above links for ideas (and Pinterest as pp said), or, check out local sure start sessions for messy play with someone else doing the cleaning up :)
Park, random walks, potter in the garden (my 17mo current fav activity), reading, local library, play dates with other mummy friends, swimming (check out local private pool sessions and get a few of you together), local play groups and toddler groups.
And of course the paid activities like jo jingles, gymboree (recommend but ours recently closed :( ) any gym based activity, socatots, tumble tots.
And if all else fails, stick on peppa pig and have a breather :grin: