go for a swim
window shopping/try on
get a makeover at a make-up counter
go to the Library take some books home
wrap up warm and go for a long walk
cinema
have a good clear out
decorating
dye your hair
manicure
enjoy your free time (what do you love to do but can't with the baby???)
Do you have a library near you? If so, go and join up. They are full of interesting books and most of them also have CD's and DVDs which you can borrow. Many of them also have a large range of popular magazines you can browse through and some chairs where you can make yourself comfortable and pass away an hour or so away.
Have a long bath and read a book. Put some music on and dance like a lunatic. My favourite when I get peace and quiet, sort out my kitchen cupboards - I love it when all the tins are lined up straight. But then, maybe i am weird!