iDraw is vector drawing tool for the Mac. It's powerful and fast, with a gentle learning curve. It filled the hole in my heart previously filled by CorelDRAW and then Lineform.
For $25 it's also a great value. Especially when compared to CorelDRAW which priced at $500 in 1993 (!), and Lineform which was $80 in 2007.
If you run a Mac and create graphics, check out iDraw.