Is there a level editor exporter kit available for blender? this would be great for level creators who prefer to use blender.
no
it would also be a lot of work, the editors for most quake engines have tools designed to work with the format
levels for those engines are stored in a format which stores the relative visiblity of each part [as in, what you can see from where], in a method which also allows things to be drawn in nearly strict front to back order [which minimizes overdraw, futher increasing performance]. The exact type is called a BSP [binary spatial partion] tree and editing of them is very well suited to CSG operations [add, subtract, intersect…] but very poorly suited to operations like grab, scale rotate [particulary proportional ones]
an exporter to any bsp tree format would have a lot of work to do. It is probably safe to assume that python would be too slow [it would take several days I’d imagine]
several days to construct a BSP tree in python?? 
I wonder how I came up with that…
well, it would be slow
oh yeah, I remember now. hl maps back on a pentium 1 could easily take over a day to calculate a BSP for [or so it seemed from my readings], and that isn’t using python.
also [in addition to not using c or even assembly] blender’s mesh format is far from the optimal geometry to generate a bsp tree from, trying to convert one [or worse: several] non-closed blender meshes into one without holes worthy of creating a bsp tree from [and with a fair amount of detail] could easily take some time, though I doubt it would be more than a couple hours [unless you run out of ram]
… I dunno, I kinda feel it would be painful, and that that estimate [several days] is wrong
aren’t there any level editors which can import some other type of mesh?
iirc unrealEd can import dxf [perhaps ase… dunno] and convert that to bsp [though you usually would want to have it as a static mesh, if it is your entire levell…]
I am not a level editor, I rant continously. must stop talking now, I have other threads to confuse myself and others on
IMHO, even usable for comercial projects, a winner combination is Quark editor and the ZHLT tools for compiling the bsp. (HL 1 bsp, ponly, but is a bsp to be used even in comercial projects) Quark is the only free editor to use in comercial projects.
If not, you could use getic3d(editor an compiler in one. But not open source, not sure either if that bsps are very standard).
Google will give very easily the links of the 3 of them.
ehm…well…
http://www.planetquake.com/quark/
http://collective.valve-erc.com/index.php?go=mhlt
If u just want to have some fun, no comercial stuff , just for mods and that…
use the Ydnar quake3 BSP compiler, and combine it with Que radiant, GTK Radiant http://www.qeradiant.com/
…or Quark editor, the one u prefer.
Ydnar bsp improved quake3 compiler (remeber, not usable for comercial projects) :
At last, while there’s an option to output bsp in HL1 format, for comercial projects, there’s only one possibility for q3 BSP ones, and is not finished, dunno if it have even half of the functionality needed. Good thing is it is open source, and in no way related with Id Tools, so free, for comercial. It seems development is a bit stopped since 2003, though :
what might work would be to make a .map exporter that would goto one of these programs and allow BSP compilation.
MacBlender
I don’t think blender would be the right tool. : When you creat a map, you must be sure that there is absolutely no space or intersection between your brushes. HL also don’t allow non planar polys. And your brushes’size should be multiples of 16. the texturing system is totally different from the UV mapping. All of that is difficult to achieve in blender.
There are lots of free and easy tools to make maps, use them 