I am working on tools for language learning. At present I still need a good Irish English dictionary.
I have written Perl and Emacs interfaces to translate.google.com for Irish <-> English translation, and abair.ie for Irish text to speech.
I have since written a program to assuage existing online Gaeilge Bhearla dictionaries into one that can be used with dictd. The bi-directional dictionaries each have about 16000-20000 entries, but still need to be cleaned up dramatically. There are other sources that could be incorporated, and one technique that has not been done yet is to use the rather large spell-check wordlists to scrape some of the online dictionaries that do not offer indexes. I may decide to attempt to strip the information from WinGléacht if this is legal (obviously not to be redistributed, but the program that does it could).
As a simple aid, I wrote a tiny script to transliterate between Irish and English.
I have a tool that defines words for you it doesn't think you know, however this relies on Word Sense Disambiguation which is inaccurate at present.