There are 6 bands with this name: 1) Beltaine - 90s post hardcore/rock from Rhode Island.
2) Beltaine Celtic Group is one of the new Polish bands playing celtic folk.
3) Czech Beltaine's music is based on a combination of doom and death metal with pagan elements and touches of folklore.
4) There is also another Polish band called Beltaine. They are from Warsaw and play dreamy, gloomy rock/folk similar to Dead Can Dance or Deep Forest.
5) Another folk project, headed by Omnia's Jenny.
6) A young band of British musicians who released a beautiful album of 5 songs called "Half Way".

Read more about Beltaine on Last.fm.