MISHA  Wired Server is a great client/server tool. I use it to access my files on my home Mac remotely, and let others I trust do the same. It has some great features like encryption and automatic updates of the search index.

It's also missing a lot of features, like threaded news, a connection monitor, and activity logging (so you can see a history of activity, etc.)

Then there are the bugs: first, for no reason, it seems to crash a lot and while you can set Wired Server to auto-launch at login, you can't set it to auto-restart if it crashes. I also have an issue with Drop Boxes—creating them doesn't always work. Also, uploading to them (and sometimes other directories) sometimes doesn't work, either. It will look like the upload completed successfully according to the transfers window, but the files will not have actually been transferred. I thought this was a permissions, but not only does it occur in folders that have the exact same privs as others that do work, it happens even on folders that you create using Wired Client.

All in all, it's great that Wired exists and is free, I just wish development was a bit more active and the application a bit deeper.  
(Version 1.3.2)

FRANSIK  Up and running in no time, secure thanks to strong encryption and free. And well, it has been localised too (English, French, German and Japanese), and provides a fairly nice user management! Simply awesome.

Of course, this is no VPN but as a Mac only software (for the client side at least) this is perfect for my purpose: exchange project-related files & messages with colleagues/ other freelancers overseas and while I am on the road (For example, you can hardly send a 150MB file per eMail that easily, and you do save time not having to explain anyone how too...).

Running beautifully on a 350Mhz G3 with 256MB RAM (Headless "Blue & White"; Mac OS 10.4.7)

Many thanks Zanka Software :-)  
(Version 1.3.1)

APPLECRYPT MODS  wow this is really great s/w and opensource too!! I'd like more from the client app but the server is amazing and a hell of a lot more mac-like than kdx! a great start!!  
(Version 1.2.5)

ANONYMOUS  This software runs an installer and places all kinds of files in invisible folders and in your startup items, etc. it may all be fine, but don't download unless you are willing to do this.

In other words, it isn't just an application that sits in your apps folder - but modifies your system behavior. I think apps should make this clear - even if they are free.  
(Version 1.2.5)

HOBY  Seems to install and work without issue. Easy, clean interface. VERY good that it's free.

It really needs isolated/discreet user folders though, in addition to the pooled file area.  
(Version 1.2.5)

ANONYMOUS  Nice program for a great price.  
(Version 1.0.2)