Here you will find some useful information about Postfix, LDAP and Samba, amongst other things.
Have a Windows 200x domain controller, and want to use Samba too? Things are a little different from the Windows NT4 days - for Windows 200x server, you now need to use kerberos authentication. Details can be found here, with an example config file.
Are you running your own mail server? Try my handy Postfix guide, with downloadable configuration examples.
There is also my Knowledgebase which contains some notes I have made over time.
Useful tools and downloads - IP Calculators / internet tools, traceroute, nslookup, whois etc can be found here.
Here is my Apache::MP3 perl module "HowTo" explaining how to stream mp3's from your own website.
Create a 'self signed' certificate for IIS web server. So, you need to have an https connection to your server, but don't want to run to the expense of a formally signed certificate? Well, create and sign your own certificate! Details here.
Also included here is a mirror of the Psion pages at ftp.cs.tu-berlin.de - data and applications for older Psion devices such as the 3a appear to be getting increasingly scarce - I found this site after much searching, hence I thought I would mirror the Psion section here.
The original site can be found here appears to be dead.