ftp://ftp.unix-ag.uni-siegen.de/pub/os/psion/ big archive of mainly series 3
stuff
http://www.mirror.ac.uk/sites/ftp.nwt.com/pub/
Another large archive
http://www.cix.co.uk/~hzk/
http://home.onestop.net/fatcatz/
http://www.cix.co.uk/~jbsoft/
http://homepages.nildram.co.uk/~nicko/
http://www.kerswell.demon.co.uk/
http://www.rmrsoft.com/
http://www.softbase.co.uk/
http://www.psion.co.at/
http://3lib.ukonline.co.uk/
http://www.geocities.com/SiliconValley/Network/6778/palmtop/psion5.htm
http://www.fnapf.demon.co.uk/atu-xviii/index.htm
http://www.system.co.uk/systematic/psion5.htm
http://www.geocities.com/psionkware