It’s better to spend one hour studying one page thoroughly than spending the same amount of time browsing 10 pages thoughtlessly.
Russianlessons has a collection of grammar points: noun cases and verb conjugation. If you need to understand these grammar points, use this website for reference.
Russianforeveryone is well organised and there you can find an answer to a lot of grammar-related questions. The website is structured as a progressive series of lessons. Each lesson has exercises at the end of test your knowledge.
Masterrussian has a little bit of everything, so it is better to use it when you already have a particular question in mind. I particularly like the page with with picture dictionaries. You can print it out and learn new words this way.
Study-languages-online covers vocabulary, grammar, pronunciation and reading. I especially like the vocabulary section. Check it out!
Russianforfree is particularly good for reading stories in Russian. Each story has a level classification: beginner, intermediate and advance. It also has a vocabulary list at the end. And if you need to see the English translation, it is also available. Each story comes with an audio file. These stories can be incorporated into your everyday practice of Russian to help you learn more vocabulary and get familiar with a variety of grammatical structures.