Jonathan's site doesn't have much to do with Bartimaeus. It's just a biography and awards and whatnot (and a picture on the frontpage that made me scream in fright when I saw a little demon emerge from Stroud's hair --- I have some lice shampoo he could use if he needs it --- not really, that stuff is expensive). There isn't anything specifically related to Bartimaeus and info regarding it.
Don't see why we couldn't have a site, but it rather depends on how much information we can place on it. The series is completed, and the only thing I could see we could really inform them about is the movie and I doubt we'd really get much special information before it's released to the general public.
But, if we can think of some things, it's certainly possible.
Gladstone/Sentynel/Krim/Gladstone/Sentynel/Krim/Stroud/Gladstone
The three ships. Kinda like the Mayflower and all those.