Hi Shane,
There's a fairly active sceen in Dublin, mainly driven by the Colleges (Trinity and UCD) but there's plenty of "private" clubs too.
I'd put the question on the Irish Freestyle Message Board aswell. The site address is
www.irishfreestyle.com. (Admin - My aplolgies if I'm not supposed to link to another site - My bad!!)
The main action is at Sluice and just about every Saturday and Sunday during the season you'll find loads of playboaters there. You can always just turn up and take your place in the essy queue. Generally a friendly bunch..
Hope this helps