NOTE: ANTIGRAV HOVERBOARDS DO NOT EXIST, so if you buy one it's a ripoff!
Hoverboards will exist someday, but looking for antigravity devices today
is like asking for airline tickets in 1903. The "Wright Brothers" of
antigravity may be out there somewhere, but their invention isn't working
yet, and you'll have to wait for years (maybe decades) before genuine
hoverboards are for sale to individuals.
Some companies say they have "hoverboards", but these are just hovercrafts
(and they are HUGE, not the size of a skateboard.) Don't waste your money
on expensive "hoverboard" plans that don't work, instead try this one:
HOVERCRAFT PLANS (free!)
http://www.amasci.com/amateur/hovercft.html