pGraph (supports nmon)
https://www.ibm.com/developerworks/community/wikis/home?lang=en#!/wiki/Power Systems/page/pGraph
RRDtool
http://oss.oetiker.ch/rrdtool
rrd4j (java RRD)
http://code.google.com/p/rrd4j/
jnmonanalyser (java nmon analyser)
http://sourceforge.net/projects/jnmonanalyser/files/