A useful feature for cases like this is the multipart/replaced content type. It allows the server to keep replacing its returned data over time, as long as the connection is open. Combined with the Javascript XMLHttpRequest it's a very powerful feature, as it allows to set a callback for when the server pushes more data.
Of course, like with most of cool Web features, it does not work in IE (works in Mozilla/Firefox though). Thus, it's a pretty useless suggestion for this case. However, for those of you that, say, have Firefox as a standard corporate browser, that's another nifty tool for writing those crazy Web apps.
Cheers!