Google talk is pretty replaceable with many other jabber based servers, and clients, and enough variance that you can generally find a solution that works best for you. afaict, Jabber messages can cross from and too the standard google talk jabber domains.

Search, I still find myself using google from time to time, but my default search is duckduckgo, this is greatly helped due to the fact that it's simple to search from google instead by simply adding !g to the search, additionally, you can do similar things for !gmaps !gimages !bing, this feature alone makes ddg a trivially better google replacement for default search.

Now, a decent replacement for the gmail client, I haven't been able to find something satisfactory web-based, or even as a desktop app. I use thunderbird for work emails, but it seems to be a little... lacking.