CPU usage graphs are now availible from the Member's site. Two graphs are displayed, one covering the last 24 hours and another covering the last 30 days.
Like the network traffic graphs, these graphs are generated in real time but the data they are based on is updated every five minutes. Endless refreshing won't increase the amount of data on the graph.
https://www.linode.com/members/graphs/cpu.cfm
A graphs overview page is available that shows CPU usage and network traffic for the previous 24 hours:
https://www.linode.com/members/graphs/index.cfm