yet I'd like to share my favorite ones:
This is the best dictionary available for Bulgarian and Greek. It works both ways and it also provides a very good language database for Bulgarian -English. I use it quite often as monolingual dictionary for Bulgarian and I even have the downloadable version in case I have Internet problems but these are rare. If anyone considers using the downloadable version, I'd advise you to buy the full one as the free version for download is missing a lot of the online/paid functionality.
BG Office Assistant (БГ Офис помощник)
This free online dictionary is created by the Bulgarian team working on OpenOffice and the language applications associated with it. It's definitely one of my favorites as it combines 4 dictionaries: a general, a technical dictionary, a dictionary of the newest IT terms and a dictionary of... a north Bulgarian dialect.
The really valuable thing about it is the technical dictionary which is not as concise as the paper technical dictionaries sold on the Bulgarian market but thanks to its search function it is the only Bulgarian-to-English technical dictionary which this full.
Oxford Advanced Learner's Dictionary
There's not much to comment about this dictionary except that it is an absolute must for everyone who studies English as a foreign languages.
It's priceless for enlightening the bedazzled foreigners who can pass CPE for example but are never sure about these new words and phrases springing up every day in the English language. This dictionary is maybe the best dictionary I ever set my eyes on and I've made sure that I always have its printed version on my bookshelf.
One of the two most respected monolingual Greek dictionaries. It was originally created by Manolis Triandafillidis who was one of the people that helped establishing the demotic Greek as today's official language. Today the dictionary is updated by the Institute of Modern Greek Studies (Manolis Triandaphyllidis Foundation) of the Aristotle Univestity of Thessaloniki. The online version has all the functionality of the printed edition and even more and this is thanks to the Institute of Modern Greek Studies. The other most respected monolingual Greek dictionary is neither online, nor freely available so I won't bother presenting it.
English-Greek Dictionary at in.gr
It's the only one bidirectional dictionary worth mentioning in this category. It's certainly better than the printed dictionaries of Oxford and Collins, so I wholeheartedly recommend it.
Webster’s Online Dictionary with Multilingual Thesaurus Translation
As you can see from the picture on the left, this dictionary provides a lot of "modern translations" to an English word. It's one of the thousands enormous dictionaries that have it all but this one is better organized, its translations have always been correct PLUS it also offers Dream Interpretation :)
(just FYI: if you see dictionaries in your dream, it would most probably mean: "To dream that you are referring to a dictionary, signifies you will depend too much upon the opinion and suggestions of others for the clear management of your own affairs, which could be done with proper dispatch if your own will was given play." Or maybe: you've done a bit too much translation the previous day:)
This is a Russian dictionary that basically has all the definitions (I mean really all) in every possible language sphere. I use it from time to time for really puzzling words that are so new that they are very far from having and established analogy in Bulgarian.
I also use a number of other online dictionaries but these are either ugly or not stable. This is why you can count on my saying that this list won't be updated unless something truly remarkable springs up.