Did you know that Gmail and Google Talk both support TLS encryption (aka SSL), rendering the data you send to and from Google secure and inaccessible to would-be eavesdroppers? Google Talk uses TLS by default, and Gmail will use it if you point your browser at https://mail.google.com (note the "https" instead of "http").
The use of TLS/HTTPS creates a secure channel between your computer and Google's data centers. This is especially important when your computer is connected to a public network, such as a Wi-Fi hotspot; I have been to conferences where people were known to use packet capture software to spy on competitors who were careless enough to communicate over cleartext channels.
I'm glad to see that Google has made security a priority. Moore's Law has made support for TLS fairly cheap from a operational standpoint, so there's really no good reason to not feature it. Let's hope TLS becomes more common in the web world.
Update: I didn't have time to check extensively, but I noticed Google Calendar and Google Docs & Spreadsheets both support TLS access as well.