Check out Gtalkr.com if you want a browser (Flash-based) interface to Google Talk. Gtalkr allows you to use Google Talk in any Internet connected PC.
The service, however, goes beyond providing a browser interface to Google Talk-it enhances it by making conversations searchable and adding an interface to label and star your conversations. GTalkr also provides you with a window to your GMail inbox.
And as with browser interfaces, you wouldn’t know if you receive a new message if you’re working in another window because the icon in the taskbar won’t flash (unless you download a client). If you want a browser interface to other IM clients, check out Meebo. (From del.icio.us)