jniThreadCPUUsage is a Java library to get the amount of user and system CPU time used per thread. This is done via JNI, which calls getrusage() on the system. getrusage() is only available on Linux 2.6.26 or later and Solaris. One useful application of this is measuring the amount of CPU time used for a servlet request. getrusage() CPU time reporting is better than using the real time clock because it measures actual CPU time used and disregards times when the thread is idle or waiting (such as when it is waiting for network I/O).
xstatbar is a minimal system stats viewer for X11. It shows stats for CPU usage (with support for multi-core processors), memory usage, the number of processes, battery usage, volume, and time. It displays as a small, horizontal bar that integrates nicely with tiling window managers.
Python System Monitor (Psymon) is a cross-platform task and performance monitor. It features global process monitoring, system load history (CPU, memory, network, and disks), disk information, network connections, detailed information and CPU, and memory percentage history per process.