I heard recently that there is now an online version of Dwelly’s Gaelic Dictionary, the most comprehensive Gaelic dictionary currently available. You can search for words via Scottish Gaelic or English, a significant improvement on printed version. You can also search for whole words, parts of words, exact spellings or similar sounding words. Another advantage of the online version of the dictionary is that you can read the text clearly and change the size if necessary – in the printed version the text is quite small and not always easy to read.
Edward Dwelly (1864-1939) was an English man with no Scottish connections who became fascinated by Scotland and learned to speak Gaelic like a native, and to play the bagpipes to a virtuoso level. He was also an active member of Comunn Gàidhealach an Lunainn (the Gaelic Society of London). He started work on his Illustrated Gaelic-English Dictionary in 1891, and it was published between 1902 and 1911. He not only compiled the dictionary, but also edited, illustrated, proof-read and printed it.
While the dictionary is somewhat out of date, the guys who digitised it are planning to add new words, recordings and images to it to bring it up-to-date.