I did a search on the forum and didn't see it mentioned, so I figured I would share something that I use everyday.
Do you have multiple computers on your desk with each comuputer uses its own monitor?
Do you have a desktop but also have a laptop that sitting next to it?
Do you have a Linux/Mac machine on one side and a Windows box on the other?
Do you need the resources of mulitple computers but want to work with them as if they were a single unit?
Do you want to keep an eye on other things while playing your favorite MMORPGs on one monitor while the game runs on the other without any slow-down? (or control 2 characters at once?)
If your answer is YES, and you want to control multiple computers with a single keyboard and mouse, then Synergy is for you. It is an application that lets you easily share a single mouse and keyboard between multiple computers with different operating systems, each with its own display, without special hardware (all it needs is TCP/IP).
At my workplace, I typically use 3 computers. Two desktops and one laptop (each have its own display). Before I discovered Synergy, if I want to control the other systems other than my primary, I typically remote control (vnc, funk proxy, rdp, you name it) to the box so I could use the same mouse and keyboard. That might be good enough for most users, but Synergy allows you to do much more!
Redirecting the mouse and keyboard to another system is as simple as moving the mouse off the edge of your screen (with no lag time whatsoever!)
Playing a game and doesn't want it to jump screens? No problem, just toggle the Scroll Lock key.
Another nifty feature is the sharing of clipboards of all systems, thus allowing cut-and-paste (text and image) between systems. Copy a block of text in your Windows box and paste it to your Linux/Mac machine, no problem. It even converts the newlines to each computer's native form so cut and paste between different OS works seamlessly. It does it all in Unicode so any text can be copied.
On top of that, it also synchronizes screen savers so they all start and stop together. If screen locking is enabled, only one screen requires a password to unlock them all.
I have been using this fantastic piece of software every day for almost a year and it definitely WOWs my coworkers. I wouldn't say I haven't encountered any hiccups (it loses the SHIFT, CTRL key once in a while), but moving the mouse back and forth from the primary screen to the secondary usually solves the problem. You may find the setup process is a little complicated at first, but try sticking with it. It's free, open source, and I strongly recommend you to try it out and donate to the author if you found it useful. Believe me, until you have used it, you don't even realize what you have been missing.
Note that Synergy is not a remote desktop application. Each system continues to need its own monitor to display that machine. Synergy just allows you to seamlessly move between the screens with just a single keyboard and mouse.
* Microsoft Windows 95, Windows 98, Windows Me (the Windows 95 family)
* Microsoft Windows NT, Windows 2000, Windows XP (the Windows NT family)
* Mac OS X 10.2 or higher
o X Windows version 11 revision 4 or up
o XTEST extension
(use "xdpyinfo | grep XTEST" to check for XTEST)
View the Full Features at http://synergy2.sourceforge.net/about.html
View What's new at http://synergy2.sourceforge.net/news.html
Download at http://sourceforge.net/project/showfiles.php?group_id=59275&release_id=379175
Before I end this mini-review, I would like to mention some alternatives that I have tried. AFAIK, Synergy is the ONLY one that has full support on all three major platforms: Windows, Linux/Unix and Mac.
Stardock's Multiplicity http://www.stardock.com/products/multiplicity/
This is NOT free and it currently supports Windows only. OS X client is in development. It has a very simple interface for setting up. The Pro version costs $69.95 but it lets you copy files/folders (in addition to text/image) between machines (something that synergy couldn't do). It allows you to control up to 7 computers (primary and up to 6 secondaries). Standard version costs $39.95 and can only support 3 PCs in total. Too expensive for my liking.
MaxiVista http://www.maxivista.com/ (what a strange name *grins*)
This app actually does a little more than the rest as it installs a virtual display driver on your primary PC, and allow you to "EXTEND" the screen of your primary PC to another one. However, although you could drag an application or a window to another PC's screen, it's still taking up the processing power of your primary (so not good for my use). http://www.maxivista.com/multi_monitor.htm
This one is also free and supports multiple platforms. But it's not as stable last I tried.
Costs $24.95. I have not tried this one.