Manifold System latest release takes it to version 6. According to the developers,  "Professional Edition is the most comprehensive, the most powerful and the easiest to use GIS and mapping system ever created.  Nothing else, at any price, even comes close." After receiving an hour long personal demo from Dimitri Rotow at GITA this Spring I think I may have to agree with him!

Here's some highlights of what $245 gets you:

• support for vector data, satellite and aerial photos, other raster images, raster data, multichannel remote sensing images, 2D and 3D surfaces and terrain simulations, multilayered maps, user supplied or automatically generated labels and a vast range of database table formats
• runs in Windows 2003, Windows XP, Windows 2000, Windows NT4.0, Windows ME, and Windows 98 and 98SE
• Import data from 80 different formats including .shp, .mid/.mif, .e00, SDTS, TIGER/Line (through 2002), DLG, VMAP/VPF, NTF, TAB, DXF, TAIF, DGN, DEM, SDTS DEM, NITF, Space Shuttle SRTM
• Integrated surfaces and terrains for 2D and 3D visualization
• Integrated map server and webmap templates
• much. much more

See http://www.manifold.net/

Of particular interest is this document titled "How do I do that in ArcGIS/Manifold" - Edited by Arthur Lembo Jr. Cornell university, the document steps through 50 "classic" GIS tasks and compares the process in Manifold side-by-side with the same process in ArcGIS... this document is a must read for anyone shopping for a low-cost GIS solution - See http://dspace.library.cornell.edu/handle/1813/165

If you ever get a chance to meet Dimitri and see Manifold live at a GIS conference I suggest you do so. He's very passionate about his product (to say the least) but a demo of all the features will leave you asking for more. Three letters sum up Manifold at release 6... WOW!

Down the road, look for a service pack to support Open GIS functionality and enable Manifold to function both as a WMS server (for those people who want to serve OpenGIS WMS) or as a WMS client (for those people who want to consume OpenGIS WMS).