I'm generating some large imagery and am trying to find a decent application that can handle these well.
I realize there are various flash based ones for viewing on the web but I'd ideally like an windows app.
I spend a lot of time experimenting and working with pretty high MP images, as I have been researching approaches and algorithms for extreme digital upscaling of RAW images. I regularly take my original 12.2mp images to multi-foot dimensions comprised of anywhere from 220 megapixels (55x44" print @ 300PPI) to 2.4 gigapixels (96x72" print @ 600PPI.) I use photoshop for viewing my work.
In my experience, with a system that has 12 gigs of DDR3 triple channel memory, Photoshop is able to handle images several hundred megapixels in size pretty darn well. When I get up to around 600-700mp or so, things start to slow down (this is when all my physical memory is consumed, and swap usage starts.) Working with gigapixel images ultimately means that you just start churning on disk more. I recently upgraded to an SSD drive for my primary/swap drive, and the performance of working with 800mp or larger images has improved considerably, however it is best if you aren't running other apps when working with gigapixel images. It should also be noted that any processing you apply to a gigapixel image is going to take some time, regardless of what that processing is...and even with a very fast system.
Microsoft has Deep Zoom (a.k.a.Seadragon, a.k.a Zoom.it, a.k.a.MultiScaleImage), which is part of Silverlight. The images need to be pre-processed by the Deep Zoom Tools or a similar tool, which breaks the image into tiles at many different resolutions, starting at a 1px x 1px version all the way up to the full version. The pre-processing will require some time, particularly for a 100+ MP image, but once it's been done, it can be very easily viewed using even a low-end system.
Microsoft didn't invent this type of image viewing, but their implementation is pretty good. The control only uses image information that's relevant to the current view, and doesn't bother to download or hold in memory every single pixel.
I don't know of any single-purpose Deep Zoom viewer program, but there could be one that exists. A Silverlight app can run out-of-browser as a standalone application (as of version 3). If you have any .NET programming experience, this would be trivial to write.
Of course, this won't be much use if you want to edit the image, but if all you're looking for is a way to open it up without bringing your system to its knees, it would be great.