A big mixed bag - choose wisely
There's a wealth of learning games here... and a dearth of distractions as well. I haven't had time to explore all the shows, but the ones I like and link to (see below) are WordGirl, Between the Lions, Word World, and Oh Noah! These shows have some great literacy games that my ESOL students love. I appreciate how Oh Noah! normalizes error in second language learning - that's one of the key attitudes I try to instill in my students, and it's great to see a first-rate show doing the same. And WordGirl is wonderful as a show aimed directly at enriching students' vocabulary. The biggest downside to this site, in my estimation, is that you can't track your students' activity. For a similar product by PBS that lets you do this, check out PBS Kids Island.
How I Use It
I link to specific games from my teacher website, based on what we're working on in class. I don't provide many opportunities to use it in class, but my students use it for home practice. Because the games aren't really adaptive, and there's no way to keep kids on task, I recommend linking to specific games rather than to the main PBS Go page or even to the homepage of specific shows. It will help to steer your students away from videos and towards games which are more interactive and learning-oriented.
I also link to several categories of literacy games, like vocabulary, reading, and spelling. You can view a directory of games by topic here ( http://pbskids.org/games/all-topics/ ) to find games in the areas you teach!