I was just reading about GoogleCL at Lifehacker and after testing it for a while I realized it's actually very useful.
Using GoogleCL - a command line tool to manage all the Google services -, you can upload photos to your PicasaWeb albums, post to your Blogger blog, modify Google Calendar events, add contacts, manage your Google Docs (upload, delete, and so on) and even upload videos to YouTube. Unfortunately it doesn't come with support for Gmail.
This can have many uses, other than the obvious ones: you could automatically back up your documents on Google Docs, completely manage your Google Calendar using a script or automatically backup your photos to PicasaWeb.
The instructions on Lifehacker are for any Linux distribution but if you're using Ubuntu, all you have to do to install GoogleCL is download the .deb file.
For other Linux distributions, download Gdata Python Client and GoogleCL source code and install it each of them using the following command (you must run it in the directory of each of the 2 packages mentioned above):
sudo python setup.py install
Using GoogleCL is very easy. For example, to upload an image to PicasaWeb into the album named WebUpd8, you would run this command:
google picasa post --title="Web Upd8" myimage.png
Please note that the first time you use each Google service, a link will be displayed on the command line - you'll have to copy this link into your browser to link GoogleCL with your Google account. But this will be required only once.
See a lot of examples on using GoogleCL, here.