I have to say my favorite thing is taking my daughter to the park and just letting her go.  There is one specific one that I like taking her to as they have slides, sandpits, lots of bridges and such and she is just non stop for like hours!  I can let her take off and not have to worry about her running off as she is constantly being entertained and excerszing.  It's great cause at the end of the day she is wiped out and sleeping is no problem.