E-messenger (now eBuddy) has been around since 2003, offers chat in a pop-up box and added Ajax functionality in February. It’s been challenged by upstart Meebo since late last year. Meebo requires chat to go on in a browser window. Both services support MSN, AIM and Yahoo, but Meebo also supports Jabber/GTalk.

These appear to be the two major players in the field, Meebo from the US and Ebuddy from Europe. Both now have VC funding, Meebo having received money from Sequoia Capital in December.

Earlier this week e-messenger fired back with an ajax implementation of its own. At this time it only works for MSN IM. Implementation is via a pop-up, whereas Meebo places the chat box within the page. There are pros and cons to this approach. With e-messenger the popup looks and feels like a normal instant messenger client, although with Meebo the page can simply be resized to achieve the same effect.