cool programs? aren't they all cool. AutoCAD umm any release... I like release 13 and 14, b/c that's what i know. but dude, if you want something to plan buildings with, you are talking engeneering, and CAD, and blue prints, and thousands of dollars! big money for that software and those types of printers
if you want to design pictures, that's a whole nother program called a photo editor. try Correl Draw, or any of the Correl suite for that matter, or Adobe's products are very nice... but i do believe for photo editing there are a few free alternatives... however i feel that they are not as powerful, it's all in what you're going to use it for i guess.