Useful online resources1. Greek-Language.gr - A wonderful online resource with a fantastic monolingual dictionary. Great for advanced learners. The website also includes information about Greek literature and history.
2. Kypros - There is an online dictionary, a spell check and free courses for beginner, intermediate and advanced levels. All you need to do is set up an account and it is free.
3. Modern Greek Verbs - Online conjugations with around 1000 verbs.
4. In.gr - You can find out about all thinks Greek here including news, culture and other Greek websites and blogs
Books1. If you have some money to spend, the most fun, interesting and brilliant for self-teaching book in my opinion are the ‘Επικοινωνήστε Ελληνικά’ (Communicate in Greek ) series by K. Arvanitakis. They cost around £20-25 each and can be purchased online or at the Hellenic Book Shop in Kentish town, London. Here, you'll fing the largest resource of Greek books in the UK.
2. The best verb book in my opinion is 201 Modern Greek Verbs by V. Christides and it can be purchased online for as little as £6.