I can think of two options off the top of my head (however, I’m not sure what you mean by router-aware).
The free answer is VNC, an open source remote control software. There are many different clients. The standard for Windows is RealVNC, and there are a few out there for OS X that I’ve used, but none that I’d recommend over the others. Google mac vnc for enlightenment.
Timbuktu by Netopia is remote control software that comes in both OS X and Windows flavors. Looks to be around $200 for a twin-pack of the multiplatform version.
Using either of these program would require you open the applicable ports on the router at the Mac’s location. If you can’t do that (and that’s what you mean by router-aware), you’ll need something web based. While I’m sure they exist, I can’t think of any web-based remote control software that’s cross-platform.
This seems to be one of the more popular OS X VNC servers.
I also neglected to mention that if you go the VNC route, you can also tunnel through SSH, making it more secure and limiting the number of ports opened. So, SSH (port 22) would be opened, and after you connect using an SSH client (like PuTTY), VNC to 127.0.0.1:5900.
Timbuktu is the expensiveware/commercialware solution, but if you can afford it, it’s worth it. I’ve used VNC and I’ve used TB2 and over the exact same computers/wires/etc at that, and it’s like the difference between a 14.4K modem and DSL. Plus, it doubles as a file-transfer protocol that’s easier to use than FTP or SMB (and doesn’t deposit OSX finderturds inside your PC directories).
Be that as it may, I’d recommend VNC if it’s just for occasional/brief use. If you need to work for hours on end and can’t tolerate delays and occasional disconnects requiring you to reconnect and pick up where you left off, bite the bullet and shell out for Timbuktu.
I recently bought a Mac Mini for work, so we can view the sites we design on a Mac.
I installed the OSXVnc server that dasgupta recommended. The computers (windows) connecting to it are using RealVNC to connect. I plugged the Mini into my router, assigned it a static IP and made that IP a DMZ. OSXVnc requires a password to connect, so I set that too. My partner can connect from his house (not on my network) and I can connect from here (on the same network). He connects using my network’s public IP address, and the router ports him right to the DMZ which has the Mini on it.
There’s instructions on the OSXVnc’s site FAQ about getting it to start when the Mac boots up. I was able to shut the Mini down, unplug it from the mouse, keyboard and monitor.
Now, when I turn the Mini on, OSXVnc starts up and I can use RealVNC to log in and use the Mini. Only “problem” is a screen at startup that tells me the Mac is looking for a mouse, but I can close that screen and my PC’s mouse works just fine over VNC.
Thanks for all the suggestions so far! VNC was the first thing I looked at, but unfortunately I need something that can automatically traverse routers on at least one end (both would be even better). Imagine a traveling Windows notebook that controls a traveling Mac notebook, regardless of the routers in front of each one*. I can’t set up port forwarding because I can’t control any of the routers involved.
If absolutely necessary, the Windows PC can have a dedicated IP address… but I don’t see how that’d help unless it was also static, which it isn’t – though I suppose dynamic DNS might work.
Hmm… looking at Timbuktu Pro, it seems that it can piggyback on a Skype tunnel. Skype automatically goes through routers on both ends, which means that Timbuktu can too. That’s EXACTLY the kind of thing I was looking for! However, $200 ($160 after Skype rebate) is a bit steep… does anyone know of a free (or cheaper) solution that can do the same thing? If not, I’ll see what I can do about Timbuktu. But again, thanks. Good suggestion.
*It’s another MomNeedsComputerHelpAgain situation. I got sick of having to help her with spyware/worms/updates/hardware/application issues all the time on her Windows PC, so I told her to get a Mac. Well, the spyware problems are gone but now I have to help her familiarize herself with OS X. Figures