Geiriadur.net

Geiriadur Prifysgol Llanbedr Pont Steffan - Online dictionary from the University of Lampeter. You can select the interface in either welsh or english, which is definately an advantage if your welsh isn't fluent enough.

Geiriadur Cymraeg ar y BBC - BBC's Welsh Dictionary -

Geiriadur a llawer o adnoddau eraill i'r rhai ohonoch sy'n ceisio dysgu neu gloywi'ch iaith. As well as an english-welsh dictionary, there are other resources for those of you looking to learn or improve your welsh.

Cronfa Genedlaethol o dermau gan Bwrdd yr Iaith - National database of terms from the Welsh Language Board.

Mae'r safle yma yn cynnig eirfa arbenigol; o wyddoniaeth i fynydda.

This site offers a much more specialised terms; from science to mountaineering.

Geiriadur.ru

Geiriadur i drosi o'r Gymraeg i Rwseg.

Dictionary for translating between Welsh and Russian.

Gerlyver Kernewek - Kembrek

Geiriadur Cernyweg i Gymraeg.

Cornish to Welsh dictionary.

Online Language Translator -

Cynnig i chwi gyfieithu safleoedd gwe i'r/o'r gymraeg.

Lets you translate website to/from welsh.