A couple of useful Linux howto's
Here's my quick and easy guide to configuring Postfix, with Spamassassin.
This is a straightforward guide to configuring Samba, in a Windows 200x environment.
And here is a guide to populating a pre-installed OpenLDAP installation with user data.
Ever wanted your own streaming server, but not wanted to use proprietry software? I use the Apache::MP3 perl module to stream mp3's from my server - although this won't work with devices such as Netgear's MP101 music player - it does have the advantage of working with any computer and with Windows Media Center. This will also stream mp's at their native bit rate (bandwidth permitting) which is useful if it's quality you're after. This is relatively easy to setup too.