Sharing your screen is better than a 1000 words of explanation, and I do it constantly both for demos and track down problems remotely. The problem is that screen-sharing software has traditionally been a nightmare to use. Apple has refined its remote desktop functionality, but it's still definitely a geek application, with a space-shuttle control panel of options. What I want is something that just works, with no messing around and zero configuration.
I've long been a fan of CrossLoop, and know Mrinal Desai, one of their founders, very well. Crossloop lets you run the app on two machines, using a simple PIN to identify your session and connect. It's still my favorite for doing one-to-one debugging sessions between two Windows machines, but I recently came across Yuuguu, and I'll now be using it any time I need to demo. What's so great about it?
Flash-based viewing. The host needs to install the application, but then any viewers just need to visit the sharing page, enter their PIN and name, and they'll see your screen in the browser. This opens the door to friction-free demos, no longer do I have to ask busy people to download and install anything before I can show them what I'm doing.
Cross-platform. Viewing is inherently cross-platform, since it's using Flash, but they've also gone to a lot of trouble to port the host to OS X and Linux as well as Windows.
Multiple viewers. You can have several people logged in as viewers, and I haven't noticed any slowdown, unlike some traditional VNCs where extra connections increase the load on your outbound traffic. This makes it perfect for doing demos or training.
Built-in IM. They've got a chat window integrated into the host and the viewer, making it simple to communicate with the attendees.
British. Ok, so I'm biased, but I remember how hard it could be to get noticed in the tech world from the UK. It's great to see them producing such an innovative product, I want to see them succeed.
I do have a few niggles of course. I wish the share URL had the PIN included, eg http://share.yuuguu.com/?pin=12345678, rather than having to cut and paste twice. The UI is aimed at a pro audience, so I found it confusing initially, CrossLoop is a lot more approachable for non-techies. The presence of two 'Show' buttons (one when a person joins, and a master one) stopped me until I realized I had to press the second one too. And the 'Person X has left' notifications seemed to appear many minutes after they'd actually closed their browsers. It would be nice to get a faster refresh speed too.
These are all just rough edges though. I'll be using this a lot for demos and meetings going forward, it's a wonderful piece of software. They'll have a booth at Defrag if you want to see it in person.