KGS Mainpage - This is the most popular client among english speakers. It doesn't have as many strong players as, say, IGS but it's a much more full-featured client that makes teaching easy. Its ranking system is robust and leniant, unlike IGS which is punishingly hard to change ranks. You want to do the Java Web Start version, if you can. This is what you would use to read all .sgf files. I play as heresiarch.
Igowin Plays only 9x9 boards, but it does it very quickly and it scales its quality based on how you do against it. It's a nice casual way to play, and it gets you good at short range fighting, without the stigma of someone watching. GNU Go The open source attempt at building a Go AI. Relative to where we are, it does a decent job. It plays at about Gus and Mark Penner's level. There are some links on this page to GUI front ends to the actual engine. I haven't used any of them. There is a fantastic Mac client, but that doesn't help much. Also good for getting a sense of play on a 19x19 setting without someone watching.
Sensei's Library This is where we are. This is basically the reason why I stuck with the game. It helped immensly in breaking through the vocab barrier. I've tried to spare you from as much vocab as I can, but all the stuff on the web assumes you know terms like hane, fuseki, seki, miai, etc. There is extensive debate about the role of these terms in modern american play. Some people argue at length about this, but do whatever comes naturally to you. SL doesn't really agree on a macro level about what to do about it, so you'll see mixes of english and asian language terms. I would recommend starting at BeginnerStudySection. It's got a little bit of everything at a level you (and me too, really) can manage.
Go Teaching Ladder A repository of real games with comments from higher ranked players. This is fabulous for seeing people make real mistakes in game situations and watching how they deal with them, along with the right thing to do considering the in-game situation. You can also submit your own games and they'll review them. A fantastic resource. You generally want to look at games played by people around your level so the concepts are reasonable.
Go Problems A repository of lots of go problems. I have mixed feelings about their interface. It has some nice features, but loading the applet for each problem blows. Another alternative for problems is the beginner problems here on SL.
Go Base This is a much higher level site. It tracks the tournament play of international professionals. It has a great replay engine that I find good for just feeling how pro games flow. It also has the tools for sgf->eps, html, png, etc that cause me to foam at the mouth. Not really useful for you yet.