An amazing new trend of game builders, possibly as a consequence of Microsoft's release of XNA, or possibly as a thing whose time has come. I'm trying to work out what it means that there are suddenly so many. In the mean time, here's a small collection of them. July 2007:

• KWorld6

Earlier:

• Age3D, 
• DXStudio,
• Multiverse,
• Qubesoft,
• Unity,
• Viscous Engine,
• Blade3d 
• Torque.

These follow on the heels of monolithic single purpose engines and tool suites like

• UnrealEd,
• WorldCraft,
• Hammer,
• Farcry,
• TheProdukkt, and
• Renderware Studio,

and more traditional engines such as

• Delta3D,
• Tao Framework, 
• Intent GamePlayer, and
• Croquet 

which present APIs to an engine which must be put together by a programmer. These can follow their lineage all the way back to such efforts as

• Dark Basic,
• The Incredible Machine,
• mFactory, and the
• Bill Budge Pinball Construction Set.

In parallel to this latest generation of tools are convergence technologies.

• Collada,
• XNA,
• Shockwave/Apollo,
• Silverlight,
• FBX,

and a great many others besides. Where is this all heading?