This is rather good: The 'official' unoffical Eisteddfod mash up.

Stwnsh 'Steddfod is a mash up website for the 2009 National Eisteddfod in Bala.

It includes

• a comprehensive GoogleMap of the town that shows the location of all events and campsites as well as permanent local amenities like cash point, petrol station and supermarket
• tweets on Trydar (Twitter)
• photos from Flickr - there's already some on there now taken by people working on site
• and most importantly (in my opinion) a list of events. The Eisteddfod's own website does on OK ish job of listing official events that take place in the pavilion and other large stages (albeit in an awkward mix of individual PDF and Word files - see bottom right on above link), but there's no central place to advertise the many small fringe events that makes the Eisteddfod tic.

This website shows that there's valuable (ok, that's questionable) Welsh language content out there that can be re-used and brought together to provide useful information. I don't think the Eisteddfod realise that it would be in their interest to help promote more of what takes place on and outside the maes during Eisteddfod week and how it can either draw new people to the festival or encourage those who visit to stay longer. If it wasn't for work commitments, I'd have really liked to be at Gorsedd y Gîcs (Geek Meet) on Thursday, but will probably have to make do with a single visit on the last Saturday.

Stwnsh 'Steddfod was knocked together in less than a week by a small group in their spare time.
If the Eisteddfod was clever, it would create o competition for next years Eisteddfod (in Ebbw Vale) for young (and old) website creators to come up with something similar, but better.

See also:
Newbie guide to the Eisteddfod (mainly in English)