I bought the T-Mobile G1 phone just a few days ago and have been browsing around Android Market, the phone's application market, quite a bit. One of the applications that I discovered on Android Market was Connect Bot. Connect Bot is a SSH Client for the Android Phone which webmasters (and other users) can use to connect to their servers right from the Android Phone.
Connect Bot is probably the number one must have application for webmasters who operate their own servers. It can be used to log into the server using the phone. For those who do not know what SSH is, it basically allows a user to exchange data using a secure channel between two network devices.
Some examples where this could come in handy would be to restart the web server, configure services or monitor the connections, processes and resource usage of a dedicated server while on the road.
The application can be installed right from the Android Market and webmasters as well as system administrators should consider installing the app right away to make use of its feature set.
ConnectBot is a Secure Shell client for the Android platform. Its ultimate goal is to create a secure connection through which you can use a shell on a remote machine and transfer files back and forth to your phone.
Update: Connectbot is still being actively developed, and it is available as an Android app for all Android devices that are currently available. The latest version of the program is available on the Android Market. The easiest way to install Connectbot is to scan the barcode over at the Google Code page to be taken to Android Market where the app can be installed.
I also suggest you take a look at the wiki on the official page, as it offers information about keyboard shortcuts and screen gestures the app supports.