Ubuntu 11.04 users missing the old ‘system load’ panel application can find similar functionality in Indicator-Multiload – a graphical indicator-applet for the Unity panel.
Fully customizable, Indicator-Multiload can display graphs for CPU, RAM, LAN/WiFi, Swap and more. Each can be assigned a colour of your choice.
A stable PPA publishing packages for Ubuntu 11.04 and Ubuntu 11.10 is available @ launchpad.net/~indicator-multiload/+archive/stable-daily.
Additionally a beta PPA is also available. The packages provided in this, whilst providing newer features – such as showing details in the Indicator menu – are likely to contain bugs. Access can be found @ launchpad.net/~indicator-multiload/+archive/daily