Skritter is great for learning kanji and words, but it can't teach you Japanese by itself. You'll need speaking and listening practice, too. Ideally, your life is full of Japanese-speaking people with whom you can practice. Or perhaps you are taking a Japanese class from a good teacher. If not, or if you want more practice, here are some resources that we think are useful.
Rikaichan is a popup Japanese dictionary extension for Firefox. It's incredibly helpful when you want to read something online, but are confronted by a wall of new vocabulary. It even de-conjugates verbs and adjectives like 考えさせられる!
Renshuu.org is a site full of unique tools for learning and practicing Japanese. It includes a library of over 500 grammar patterns with example sentences as well as quizzes and review tools to help you prepare for the JLPT, Kanji Kenetei and more.
All Japanese All The Time (AJATT) is a powerful site run by Khatzumoto, who taught himself to seriously rock Japanese and is also learning Mandarin and Cantonese. The site is like a pool of motivation in which you should jump, regardless of which language you're learning.
Myngle is the multi-award winning destination for online learning. Learn Japanese with professional native teachers, specially selected and trained. They've got a large and growing network of teachers and students.
Omniglot has a truly great collection of pages you should read through if you are new to the language and want to understand the basics. The explanations are comprehensive, the writing is accessible, and there are lots of good examples.