We live here in Sardinia half-way down the east coast and there is a good and developing MTB scene:-
1. MTB races Oct+Nov (they have road races all summer)
2. 5-day enduro rally each year in June, with 25 people in 2008, 50 people in 2009,…
3. excellent "exploratory" riding on firetrails, rough limestone shepherds' tracks,…we live in the wildest part of the island
4. we have people to come to stay to do mountain biking: 2 Belgians this evening, 3 Sards on Saturday, 2 English people today who've hired bikes(We run a guesthouse for outdoor sports people, the MTB page is here) I try to go riding with guests – there are plenty of places you wouldn't go by yourself (no mobile phone coverage, no people,….)
There is quite a lot of info, photos, videos you can download from our site which gives you a good feel for the riding here. In fact, the MTB part of the site needs updating since more and more people are coming, this is a job for November…the new stuff is in the blog. As regards the rest of the island, Skedaddle do tours, and there is a good MTB scene in Cagliari.