Any suggestions? As Illustrator is kind of out of my price range... At the very least, I just need something which can take an .eps and produce an .ai file.

There are a couple of open-source vector programs which run under X11 -- Inkscape and Sodipodi. Inkscape is nice, but I don't think it'll do the conversion for you... I don't have Sodipodi installed to check it for you.

The various tools that come with GhostScript might also help with converting EPS files... but I doubt they'd work with .ai files.

Is .ai an open format? I seem to recall it's basically postscript anyway...

There is a question asked before on this topic, so try a search. Failing that...

Create by Stone Design is highly recommended.

Look at Deneba Canvas, CorelDraw, and perhaps Omnigraffe.

Graphic Converter should also work with .eps files.

And check...
http://www.artage.com/pages/products/products.html
http://mac.softpedia.com/public/cat/19/19-782.shtml

And of course, check some CAD apps like...
http://www.ribbonsoft.com/qcad.html

CorelDraw and the rest of their studio for mac is canceled

http://www.microsoft.com/products/expression/

Free and good. Used to cost like $300.

Thanks diordna, that's exactly what I needed (for importing free form geometry to Wings 3d.)