Links

www.masterrussian.net **
Online discussion forum about studying the russian language, with hundreds of topics and thousands of posts. Many interesting discussions. Too bad that some posts contain interesting questions but no conclusive answers and that other posts are filled with typos and gibberish. But by and large this is a useful ressource and I recommend it.

russian.dmll.cornell.edu ****
This is a great website for improving your Russian online and for free. The people at Cornell have prepared segments of Russian 1970's movies with transcripts, vocabulary lists, grammatical comments and of course, streaming video. Great stuff! Obviously studying a language only online has definite limitations, but the movies are so fun and you actually get to understand each and every word. You can also access the dialogs they use for the Russian curriculum, complete with audio files and word lists, but this is probably not the most convenient way to study Russian.

Online Dictionaries
There are several free online Russian dictionaries, some of which are quite good. Unfortunately, no one has an audio link with the actual pronunciation like on Yahoo Reference. If you make flash cards with your computer, you can cut words and definitions from these online dictionaries and paste them in your program. Fast way to build up your flash cards. My favorites are:

www.rambler.ru ***
I use this one a lot, although it does not find everything and when you enter a perfective form, it will only list you the imperfective. You then need to cut and paste the imperfective back in the dictionary to get the translation.
www.lingvo.ru ****
Finds almost every words I search and lists plenty of examples.
www.multitran.ru ***
Is probably the most complete, but not the most straightforward to use. Definitions, idioms and even an usage database where you can see dozens of actual examples of the word being used.
www.yandex.ru ***
Can also translate from/into Russian in French, German, Italian or even Spanish with an easy-to-use interface.