For web design / AJAX, look immediately at Mootools... you just import the file(s) at the head of a page, and then you've got lots of simlpe commands and effects at your fingertips. An easy way to make AJAX calls, and feed the response from the server into a js function or another mootools function for example. You can animate things around the page, fade them in and out, add new things to the page (DOM tree), remove things from the page, play with CSS on the fly... it's good shit.
You can download the full thing here -
http://mootools.net/downloadOr just include the parts of mootools that you need by customising a download here -
http://mootools.net/coreThe docs to help you get started are here -
http://docs.mootools.net/Another set of APIs to look at is over at google
http://code.google.com/more/#products-featured-androidGoogles Web Toolkit, AppEngine, etc are all increasingly popular alternatives to things like MooTools - something that helps you turn your site into something dynamic, more of an application. Then they've got things like OpenSocial, which from what I gather, is a starting point if you wanted to get into developing for MySpace / Friendster / etc or creating your own social networking type thing.
I've been looking at the Facebook API(s) recently: FBML, FBXML and stuff like that.
I've been trying to make a site called InviteMii -- a community site that will help with the lack of a friend requesting feature on the Wii and the DS, help you organise online games etc. If I can get this thing finished, I am looking at having a Facebook application/plugin, so people could swap friend codes and use my site's functionality directly over facebook. I need to finish the site first though, I really should get back to it this week. I don't think I'm that far off.
I'm going to make a separate thread about my site actually, because at the moment - I am the only person working on it and I could use some help.
I can't offer money for help though -- and the reason is largely that I'm poor enough as is, a lot of work is already done, and I don't intend to commercialise the site with adverts and stuff if I don't have to. If there's one way to attract the attention of Nintendo's lawyers it would probably be by making money off a site that allows people to re-create their own Miis and message each other over the Wii's messaging system. What I can do though, is permanantly have you on-board with the site as a staffer when its finished, give you credit and priviledges.
If anyone is interested, let me know, or look out for the thread I'll be making.