What can I do over the summer to keep up strength and flexibility for ballet? (question directed to Mintchip)?

I'm serious about ballet, but I'm not going to become professional or anything. I have currently been dancing en pointe, and my ballet classes start again in August. I'm not doing any ballet classes over the summer, because I can't afford it. I have been doing six hours of ballet a week, and I can do my left and right splits. I have average extension, but I am afraid that I will lose my flexibility over the summer, and I don't know what to do at home to keep up my strength.