Yet another much requested AppIndicator is now available for Ubuntu 11.04: an indicator to display the network speed as well as CPU, Memory usage and more called System Load Indicator (or "Indicator Multiload").
This is a port of the original System Monitor GNOME Panel applet to appindicators and Vala. This means it has most of the features the System Monitor Applet had: display processor, memory, network, swap space, load or hard disk activity, change the colors and so on using an Ubuntu indicator..
There's one catch though: because Ubuntu appindicators can't display a tooltip, you won't be able to see the actual network speed, CPU and Memory usage and so on but only a graph. For a more detailed CPU / memory Ubuntu AppIndicator, see: System Monitor Indicator Puts The CPU And Memory Usage On Your Panel
sudo add-apt-repository ppa:indicator-multiload/stable-daily sudo apt-get update sudo apt-get install indicator-multiload
Once installed, launch System Load Indicator from Dash.
Important: System Load Indicator is still in alpha! Report any bugs you may find @ Launchpad.
Also see: Indicator-Sensors Displays CPU / Motherboard Temperature On The Panel Using An AppIndicator [Ubuntu]