nmon is an excellent performance monitor for Linux systems.
Since Amazon Linux AMI is compatible with RHEL5, I've downloaded a binary RPM from:
http://pkgs.repoforge.org/nmon/
$ wget http://pkgs.repoforge.org/nmon/nmon-14g-1.el5.rf.i386.rpm
$ sudo rpm -ivh nmon-14g-1.el5.rf.i386.rpm
not working