Here is a selection of homepages, all of which have pages or programs for the series II.

John Allen's Software Showcase contains a program to connect to an Acorn RISC computer, via the standard comms link.
Daniel Dubocq's homepage. If you can read French, read the French version of this page (his English is very poor). The only thing for the series II are some books he has written (also in French).
Andy Grieve's Homepage . He has a Psion program called ListEdit here.
Christophe Guilloux's homepage, in French. He has a few Psion programs here, as well as a French OPL guide.
Helmut Heller's homepage contains a program to include holidays in your LZ diary.
Peter Hunkeler's homepage. He wrote the FileXFer utility our pages, and this page is his 'contribution to the Psion World'.
Chris Parker's homepage contains piloting software for the LZ (and later Psions).
Peters Psion Sidor, a Swedish Psion II page. It has a few programs, including the Psion emulator from the developer kit. This page can also be found here
Jonathan Philpott's Homepage contains very little at the moment, but Jonathan will put any programs he write here.
Glyn Pollington's Homepage. Glyn wrote the Trivia and Border programs on our ftp site. He has a few more programs available here. His page uses frames, so you can use this page if your browser doesn't support them.
Paul Robson's page details his progress in making a real Psion II emulator. I for one am looking forward to seeing this in action.
Zac Schroff's homepage also has a section, on which there are some Psion II programs.
Brian Smith's Homepage. Brian wrote the cross assembler available from our site. There is also the Scrunch utility which removes indentations and REMs from procedures written on a PC.
Totally Trygve is Trygve Henriksen's homepage. He has converted a Psion II into a bike computer by connecting it up to a sensor on the wheel, and writing a program to calculate speeds, distances, averages etc. His organiser 2 section is here.

Now a list of sites with in-depth information about the Psion hardware, and further sites with software.

Farnell. Here you can find the hardware specifications of many chips, including the Hitachi HD6303X which the Psion uses. It is in Adobe Acrobat format. The hardware chapter in Aitken's book is an extract from this.
The Chip Directory has information on a huge number of computer chips. The instruction set of the HD6303 can be found here.
Ian Harries' page in depth page about the HD44780, the display controller which is also used in the Psion II. It contains amongst other things a cleverly designed set of UDG's to display large numbers, and the complete character set of the CM/XP.
ftp.demon.net and ftp.sonycsl.co.jp are ftp sites containing lots of old material for the series II. Most of the files are compressed in one of several different formats, so it is not very easy to access.

Various pages which mention the Psion, and the many ways it can be used. Companies that use the Psion in their products are also included here.

Bob's computer museum contains a page about our beloved machine.
London Life Archive has another story about how Psions can be used.
A small article about using the Psion as a pollen counter.
Cygnus Instruments use the Psion LZ64 as a data-logger for their 'CYGNUS-3 Ultrasonic Thickness Gauge. Nice colour scheme!
Hanson Survey & Design Ltd. use the Psion as Atod converters / Survey Meters.
Microtima has an interesting real-life use for the Psion LZ64, viz. programming traffic signal boxes.

A list of links to companies that sell Psion II related material. The fact that a company has been included here is not necessarily an endorsement. Also, be aware that many of the prices here are very high....

NEW Blackroc Technology Ltd.  Is a Psion distributor which retails a varied range of  Psion products and accessories including a limited selection of Organiser II's and  peripherals. Blackroc specialised in providing organisers in rubber cases for outdoor applications or humid environments.
Arktech Ltd. Provide a series of programs designed to allow a land surveyor to interface the Organiser II to a variety of Total Stations (also know as EDM's - Electronic Distance Measurer). The software, known as Arkive, is supplied on a Psion Datapak. The company does not yet have a website but does have e-mail; arksurvey@aol.com. It's normal address is Arktech Ltd., 20 Westgate, Tadcaster, North Yorkshire, LS24 9AB, Tel:01937 834445
Dyna-Sys. Expensive, but they do have a lot of stuff.
Farnell. One of the very few companies in England that still sell Psion II hardware. Approximate prices in pounds are: 150 for LZ64, 120 for XP, 60 for Comms Link, 25 for 32k datapaks, 55 for 32K Rampaks. Prices are lower for larger quantities.
Geodos The homepage of the GeoDos Surveying program. It was originally developed on the Psion II and still available for these machines.
Kador. Company that produces rubber keyboard covers for computers including Psions.
Raco Industries. Sells some Psion II material here.
RVS Software (USA). Is it me, or is this ridiculously overpriced?
Measurement Technology Ltd. sell an LZ64 which has been repackaged and renamed the MTL611. It is used for 'on-site hazardous-area data transfer and transmitter configuration'.
XEComputer Products (USA). A nice page with a good range of products.

And finally, some pages which have more to do with later series of Psions.

Psion 3/3a Programming reference. Much of the OPL on the series II is also used on the series 3, so these pages can be of some use. Here is a short summary of how the OPL language has changed from the series II to later machines. The same page can also be found here or here.
The 3Lib pages is a good starting point if you ever get a series 3 or 5. Here it has a page for buy/sell ads for Psions, though these are also mainly for the series 3 and 5.
Brian Clegg's page contains a really neat comparative review: Psion Series 5 vs. Hamster!