Lawrence Hall of Science - very cool. Good games for kids. I did "Aphid Eater." I might get better with practice, but it was confusing the first time through, and I lost the game very quickly. Probably needs better instructions, or else improved programming.
Virtual Museum of Canada - very educational. I looked at an online exhibit on "1759: From the Warpath to the Plains of Abraham" which I guess would mean more to me if I was Canadian. It works pretty well with broadband. Seems like a pretty good way to explore a subject online, i.e. pretty good use of technology to simulate a museum exhibit on a topic. Not the most fun, but not bad.
Exploratorium - probably my favorite. I did "Frog Tracker" and it was fun and easy and also educational to get a whole chorus of frogs going, and then to change it to include other frogs. Quite musical, too. Could maybe have more educational content, but there are a lot of choices here -- "Frog Tracker" is one of maybe 50 on the menu. Lots to explore.
Natural History Museum - ok. I did Velociraptor in 3-D and Volcano. Volcano taught me a few things I didn't know about volcanoes, but the graphics are kind of dull and uninspired, esp for volcanoes.
Nanozone - good. Seems a bit dated, but fun to use. Could improve the navigation without much effort. I did "The Case of the Green Milk." Has a kind of personal, neighborhood community museum feel to it.
Monterey Bay Aquarium - I did "Sea Otter Interactive" and "Deep Sea Memory Game." Both are a little simplistic compared to, say, Exploratorium, but still are fun to use and work well and make their point effectively. They might want to change the grade levels as I found "Sea Otter Interactive" informative even though it's for K-8.
UCMP Berkeley - I did "Adventures at Dry Creek." I liked the kind of adventure game format very much. Very good application to get the most out of the technology, i.e. you don't have to be ultra-flashy if you design things right.