It's probably worth mentioning my onevent mixin here. http://tapestry-stitch.uklance.cloudbees.net/oneventdemo
Sorry to toot my own horn but I think it greatly simplifies many ajax interactions. It not only allows a context to be passed but it can also send a list of clientside field values in the ajax request. Currently you can only listen to one event per dom element. It would be nice to improve it to attach multiple listeners to multiple a single dom element. Does anyone else think this should be part of tapestry core? NB I think the "onevent" name is ambiguous. It could do with being renamed to "observe" or "listen".