The Ultimate Free Network Applications:

With just five applications--five, free applications--you can do anything you ever wanted to do across a network connection.  We're serious.  Using these applications, you can bridge your computers together from anywhere in the world across a secure, hacker-proof connection.  From there, you can dial into your desktop as if you were sitting right in front of it, looking at the exact screen you'd be seeing were your butt in the groove of your favorite office chair.  If you're a hardcore network enthusiast, we'll even show you how to tab-browse through multiple, connected desktops as if you were pulling them up in Firefox or something.

LogMeIn Hamachi

 

What it does: We really hate recommending LogMeIn Hamachi all the time.  It just feels like we're using the same ol' program every time we run any large networking story.  But try as we have to find a better alternative to LogMeIn Hamachi, there simply is no better way to connect two computers over the Internet, hassle-free.  Rather than having to fool with managing a computer's internal IP address, external IP address, port permissions, and what-have-you, Hamachi turns this headache-inducing networking configuration into a one-button step.  Fire up the program, create a group for your connected devices, and run LogMeIn Hamachi on any of the computers.  The program sets up a secure tunnel between your connections, giving each device its own, unchanging IP address.  You can then connect to your other desktops for any number of purposes, be they the programs listed below, LAN gaming, or anything.  LogMeIn Hamachi is the ultimate networking foundation.
Download it here!

UltraVNC

What it does: Although we strongly recommend you use the previous program to set up your network before firing up UltraVNC, you can use this awesome networking application to connect to any computer with an IP address.  Once connected, you're looking and interacting with the computer's desktop as if you were sitting right in front of it.  You can also establish file transfers, chat with whoever it is might be sitting at the terminal, and utilize a variety of compression mechanisms to maximize your session's performance regardless of what speed of connection you're using.  A number of "VNC" varieties exist on the Interweb, but we have found the most success (and usefulness) with UltraVNC.
Download it here!

Terminals

What it does: So you liked UltraVNC, but you have more than one computer you're planning on connecting to at once?  No need to fire up a bunch of UltraVNC sessions--not when you have terminals, that is.  This is the tabbed browsing program we mentioned previously.  It's a great way for the hardcore network enthusiast to manage multiple networked screens at once, and it comes with a bunch of system administrator network tools built into the application for easy access.  You never know when you might need a Trace Route...
Download it here!

Live Mesh

What it does: Live Mesh lets you pull off the same remote desktop features as Terminals and UltraVNC, but the true strength of this application lies in its powerful synchronization features.  You create a mesh, which is a grouping of computers and users who all receive special access to a batch of files.  To create this batch, you assign folders on your computer to serve as Mesh Folders--anything placed in them gets synchronized to the devices in your Mesh.  It's a great way for keeping your files and folders organized across multiple devices--even better if you and your friends like to share a hot batch of jams amongst each other.
Download it here!

Advanced IP Scanner

The name of this application should give away its features, but there's more to this helpful program than you might think.  Not only will it scan through a class of IP addresses and tell you details about all the computers it sees, but  it lets you perform simple--but powerful--commands on the network devices you find.  Throw them wake-on-LAN commands, shut them down remotely, and connect to the computers (via Radmin) at the touch of a button.  If you're running a large network of PCs, put this program on your "to-install" list immediately.
Download it here!