Festival dates so far known for 2010 go like this

Fishguard Folk Festival - May 28-29-30-31

Coastline Bluegrass Music Event - June 3-4-5-6

Raglan Music Festival - July 11-12-13

Wakestock - July 2-3-4

Small Nations Festival - July 9-10-11

New Quay Music festival - July 30-31-Aug 1

Gwyl Pontardawe Festival - August 13-14-15

Croissant Neuf Summer Party - August 13-14-15

Green Man Festival - August 20-21-22

Feanol Festival - August 27-28-29-30 unconfirmed

More dates will be added as I get them.  If you have any information not here let me know.