graphics package advice needed

Hello all you lovely, lovely people. (Er, I'm after some helpful advice.)

Does anyone know of any freeware graphics/desktop publishing software that I could use on my mac? It's bang up to date in terms of OS. Before being self-emplyed I used to use autocad, (via an incredibly talented technician to be honest), to create plans and images of landscape designs for clients) but I can't justify shelling out for expensive software now that I work for myself as a self-employed horticulturalist and I don't really do that much garden design (yet...) Currently I'm 'reduced' to pencil and tracing paper and occasional trips to the local office supplies shop for scanning/copying but I just wondered whether anyone know of any little packages out there that might help. Thank you, (he says optimistically).

I use paid up software so I'm not that experienced with the free stuff but I know people swear by Gimp as alternative to photoshop.t

Sure.

Google Sketchup
Inkscape
Autodesk Sketchbook Pro (£2 a month) + Wacom Intuos (£50 @ Amazon)
GIMP

Autodesk Education site, everything including AutoCAD for Mac free for anybody self teaching

Cheers guys. I've got sketchup - just never got my head around it. Will take a look at the others. Many thanks.