Timbuktu Pro is a complete remote access solution for the Macintosh-- and for Windows, for it is cross-platform. Not does it allow you to transfer files between two computers, but it uniquely gives you the ability to control a remote computer as if you were looking at its screen, typing at its keyboard, and moving its mouse. In a sense, this makes it the ultimate collaboration/support tool, because it allows you to see what another person is doing on a remote computer, to take over for them, and to actually communicate with that person via a chat window or "flash notes" (messages which are sent to the remote computer) or by actually talking to them thanks to the intercom feature. Finally, it is extremely flexible in terms of how it allows you to connect to that remote computer: you can be linked over the internet (through your internet service provider) or over a LAN (AppleTalk or tcp/ip), or using AppleTalk Remote Access, or even directly via modem-to-modem connection.
I almost always use Timbuktu Pro to connect to my office computer (a PowerMac 7200/90) from home, and thus use regular PPP internet access that my university gives us. Before establishing any connection to the remote computer, it must first be configured for different types of access by different users.
First of all, you can set a "master password" which can be required if one wants to change the Timbuktu Pro configuration, by altering preferences, toggling incoming access on or off, etc. Then you use the familiar (from Apple file sharing) "user metaphor" :
As you can see, you can have different "accounts" for individual users, but also define general guest access. The system is so flexible that you can determine whether any user may "Ask for Permission" to obtain certain access privileges which s/he is not normally allowed.
The new user dialog gives a good idea of the different ways in
which you can use Timbuktu to gain access to a remote computer. 
Once Timbuktu has been configured for access by different users, you can proceed to connect. The dialog to control a remote computer looks like this:
Once you hit return, magic occurs: a window appears on your Mac which is an exact replica of the screen of your remote Mac! If the screen resolution of the remote Mac is larger than that of your local Mac, you can use the scrollbars and/or have the image scroll automatically as you move your mouse. Another useful viewing mode is invoked by clicking on the upward- and rightward facing arrow in the top right-hand corner of the screen border: the remote Mac's screen becomes literally superimposed on that of your local Mac, almost giving you the impression that the remote Mac has merged with your local Mac (note that the full screen of the remote Mac still cannot be displayed in its entirety, because the resolution of my remote Macs monitor is 632x824, while my PowerBook 3400/180 offers 800x600. Basically, everything you do within the remote Mac's window affects it as if you were typing on its keyboard or moving its mouse (you can even drag files into and out of the window in order to transfer them), with two important exceptions: first, over a 33.6kbps modem connection, you will notice a delay when typing or when the remote Mac's screen updates, and second, if you wish to paste into a window or dialog box on the remote Mac, you must first send the information from your local Mac's clipboard to the one on the remote Mac. That is the purpose of the second and third icons from the top on the right border of the Timbuktu Pro screen.
Of course, Timbuktu Pro is not merely limited to control, observation, and voice/text messaging: it offers powerful file transfer capabilities:
Netopia (formerly Farallon) claims that file transfers over an ethernet LAN (10 or 100 megabits/second) are significantly faster than using AppleShare IP. Over our departmental (10 mbs) network, I get throughput approaching 800-900 kilobytes per second.
You can even search for files on the remote Mac:
You can download an evaluation copy of Timbuktu Pro. A spec sheet is here.
You can currently purchase Timbuktu online. Normally, you purchase what Netopia calls a "twinpack" -- a licence for 2 copies of the software for your local and remote machine. The download price is $139.95. You can also order a boxed version online (the software is actually on CD) for $189.95. I strongly urge you to investigate whether your university has a site license: a twinpack of Timbuktu Pro 4 costs approximately $70 for faculty, staff, and students of the University of Texas at Austin. It was also available for $70 during MacWorld Expo in January, so you might consider waiting until July for the next Expo.
Installation
This is easy, although the CD installs a fair amount of software, including the Timbuktu Pro extension (which puts up a system-wide menu between the clock and the application menu), "plug-ins" which also go in your system folder's extension folder, and the Timbuktu Pro application. You must restart in order for Timbuktu Pro to work.
Advantages
Timbuktu Pro is a tech support person's dream, and it also offers the widest variety of connection methods and well-developed file-transfer capabilities. It basically gives you the ability to manipulate a remote computer as if you were there.
Disadvantages
Timbuktu Pro installs a necessary extension, and I suspect that it may, on rare occasion, contribute to system instability (I usually run my Mac with the extension disabled). It does not integrate seamlessly into the remote Mac's file system in the manner of ARA or ShareWay IP, but this disadvantage can be circumvented, for example, by transferring a software installer and running it there.