How about a twmpath (Welsh ceilidh)? Lots of bands and potential interval acts on the trac-cymru website Sian mentioned. I was debating inserting a subtle plug for the St David's day(ish) ceilidh with Derwenna and Martyn Harvey that we're running in Sheffield on Saturday 4th March, but decided I couldn't get away with it and will probably start a new thread about it.

The format for our event (which is in association with Sheffield University CeilidhSoc, so a lot of our target audience are students/recently ex-students) will involve what we describe as 'anglo-welsh ceilidh', with some Welsh interval acts, and real ale and leek soup being served.