BeGeistert is the traditional bi-annual meeting point for the international Haiku user and developer community. The week after the BeGeistert weekend, a coding sprint will be held. Maybe there'll also be another workshop for aspiring coders on Monday, which would be charged separately. All in the same location in Düsseldorf, Germany.
Registration is now possible at the BeGeistert.org website.
The BG-weekend is 35 EUR including lunch. A night bed & breakfast in the youth hostel costs about 25 EUR.