Good place to start?

Well, you guys may have remembered me from several years ago, I learned a fair amount but always had trouble with particles. I haven't studied since then (years now) and want to go back in. Does anyone know of a site which has grammar that makes it easy to understand? I have the hardest time understanding when to use 'ni', 'ga' vs 'wa'.

I have to start from scratch I'm afraid, I have all the hiragana memorized still etched in my brain, and I know probably 20 kanji by heart. I know some katakana, but not much. I seem to remember playing a katakana game in the past at like a flash site, made learning it easier.

I really want to learn to conjugate verbs to make sentences again..

Any suggestions on where I Should start? Know of any good websites?

Thank you

A good resource that could probably help you sort out some of your grammar and particle issue is this book.
Amazon product ASIN 4789004546
a little bit pricey, but worth it if you are serious about studying. I would say the only drawback is that it can be a little too thorough and cause you to get sidetracked trying to learn the details about one little thing. Avoid doing that and give yourself proper practice (verbal, written, and listening) and it should be a good help to you.

I'd like to share some material... | Japan Forum

This thread has pretty much everything you need and having Tae Kim's site as the first one is a very good choice indeed ;-)