Weekend fun (in DC) on a budget

I love Fridays, and the anticipation of the weekend that stretches ahead of me. It will be even nicer if the weather decides to cooperate and we don't experience heavy rain fall which has been frequent in the Mid-Atlantic region lately. I want to do some fun things this weekend, but I want to spend minimal money. Here are a few ideas I have:

• Go to Artomatic. Artomatic is a month-long art festival that starts this weekend in Washington, DC. It looks like it might be fun and there is no entrance fee.
• Wander around one of my favorite Smithsonian museums. I love to visit the museums, and want to pop in to visit a few before the really hot, steamy weather sets in.
• Head to the library and check out some free books, music or movies. My local library has a decent selection of movies and books, so I don't usually leave the library empty-handed when I visit.
• Go out for appetizers instead of a full dinner. It would be fun to go out to eat, but a full dinner could be pricey, ordering just appetizer's would be cheaper.
• Bake something. I have a taste for some cupcakes, so instead of buying them, I could try to make them myself. This won't be a free activity, but it shouldn't cost that much.
• Head to the gym and take a class. Since I already have a membership, I should use it right? It also just dawned on me that swim suit weather is just about here...

What fun things do you like to do in your area that cost little?