For a whole range of interactive lessons for all levels, check out: LearnGaelic.net
After searching for ‘Abair! : faclaír’, the only Gaelic dictionary that my tutor recommends, online for a while it looked like I was going to have to do a long and probably futile crawl around second-hand bookstores. Or just agree to pay anywhere between £23 and £2500 (really!) for a book which should cost £5.99.