Come and practice your programming. Learn some new things and try out something you'd never do at your day job.
What is coderetreat?

Coderetreat is a day-long, intensive practice event, focusing on the fundamentals of software development and design. By providing developers the opportunity to take part in focused practice, away from the pressures of 'getting things done', the coderetreat format has proven itself to be a highly effective means of skill improvement. Practicing the basic principles of modular and object-oriented design, developers can improve their ability to write code that minimizes the cost of change over time.

Details on the website:  http://coderetreat.org/
Specifics on what a typical coderetreat day is: http://coderetreat.org/facilitating/structure-of-a-coderetreat

The coderetreat day consists of 5-6 sessions, each session's learnings building upon previous sessions. The morning focuses on becoming comfortable with the problem domain, breaking old habits and beginning focused self-discovery. The afternoon pushes the envelope by challenging pairs to stretch their skills and understanding of abstractions, modular design and test-driven development.

Global Day of Coderetreat joins cities across the world in coderetreat, all on the same day.
Money is to reserve your spot and will be refunded when you show up.  If you don't show up, it will be donated to some programming related cause.