Untill Unity 3 comes out (I bet you could make better maps than UE3) is there a way to make maps in UDk and import them in to Unity?
This is a very board question
No, there is no way for that.
UE uses a BSP alike format that works only within UE
Well, you could create your level geo using BSP, and save it out of the editor as an OBJ.
When exporting to an OBJ, there is no concept of additive, or subtractive, geometry. What you get is a mass of everything as geometry. Meaning a lot of cleanup work in your 3d app of choice.
This is also coming from the actual UE 3 Editor, not the UDK.
It doesn’t seem worth the effort.