Redshiftgui changes the color temperature of your monitor to better match that of your surrounding. This means that it sets a cooler color temperature during the daytime (due to natural lighting) and sets a warmer temperature at night (due to indoor lighting). Similar to f.lux, this is a GUI port of the redshift project.
rmlint is a command line tool to clean your filesystem from various sorts of lint, such as duplicates. It tends to be much faster than fdupes. Additionally, it is able to find empty files and directories, nonstripped binaries, files with the same basenames (nameclusters), old temporary data, strange filenames, and bad links.
PerfMonger is an yet another performance monitoring tool. The monitoring targets of PerfMonger are similar to the ones of sysstat (CPU usages, IO usages, etc.), but PerfMonger can collect and report performance information very frequently (the reporting interval of sysstat is 1 second at minimum, but PerfMonger can use a much smaller interval such as 0.5 seconds or 0.01 seconds) and can display performance information in both human-readable and machine-readable formats.