Their sign says, "Eet, drink & spellencafé".
My interpretation, being linguistically challenged, is that this is a cafe where people eat, drink and spell. Instead of Karoke contests they have spelling bee's. You get a free drink if you can spell certain words. If two people get into a drunken argument instead of challenging each other to fight they challenge each other to spell.
I think they play darts and possibly games involving dice and a roulette wheel as well.
Postscript April 2008 - Thanks to Sylvie, now I know "spellen" in Dutch means "play" - it's a cafe where you can eat, drink and play.
Sounds good...
The Official Holland Site - Netherlands Board of Tourism & Conventions (NBTC)