Pay off any outstanding debts. Help your parents out if they need help with anything (within reason).
Take 20K and spend it on a four month vacation where you don't have to stress about anything and unwind from running a startup.
Use the rest of the money to start a new project where you don't have to raise any money until you have a solid proof of concept or even positive cash flow. Or don't. jwz bought a nightclub instead of staying in software, and he seems quite happy with his decision.
Read Derek Sivers' blog post on what he did after selling cdbaby: http://sivers.org/laboratory
Just because you had one startup exit successfully doesn't mean your next one is guaranteed success.
Just because you have no guarantee of further success, does not mean you should not try again.
Congratulations, and good luck!
This brings up an interesting question, what would you do if you didn't have to worry about money? Let's assume you're set for life and can live whatever lifestyle you choose for the rest of your time on earth. What do you do then?
Congrats and ATB for future venture.
The relevance of this answer might depend on your location though