I've been constantly running one or more text based games at a time online for more than a year now, and I find google documents work like a charm for this. Way less clunky than a proper forum. We write in a two-column table in a regular text doc, with fiction text to the left and ooc text to the right - both for rules talk and for cheering each other on. It also has a built-in chat and simultaneous editing, which does a lot of good as well.
The game pace goes up and down over the weeks, of course. Sometimes, when everyone is at their comps - or with our smartphones at the ready - the game runs really fast. (I love sitting in the sun, playing on my phone, or playing on the subway, or during breaks at work, or wherever!) At other times a week goes by without a single move, which is okay, because everyone is too busy now and then.
Sorry to sound as a sales text, but I'm having so much fun with this. We've been playing much more this way than in several years face-to-face before we started with this. :)