I recently ran across a great program on the net for drawing schematics. The two reasons I call the program great is because first and foremost, it is so easy and a pleasure to use, and second, it is a free download that you can virtually use forever once you register the product.
The program is called Design Works Express for the PC and Design Works Lite for Mac, and both programs can be downloaded from the company which owns the software from here: http://www.capilano.com/html/downloads.html
Update 9/28/2012: The program is no longer offered for free from Capilano, but I would still recommend their software. It worked well for me, for my project.
The reason I acquired the software is I am in the design stages of building a a Transceiver/Amplifier key-line interface switch box for my station. Having the ability to do a unlimited number of circuit changes before I even pick up a soldering iron is invaluable, and being able to make the changes with the click of a mouse key is priceless, when compared if I had to do it the old way using pencil, paper, and an eraser.
I highly recommend the PC version of the software. However, I cannot comment on the Mac version because I have not used the program.
Once I get the circuit finalized and building begins, I will post the schematics, parts list and more information about the operation. However, the goal is to allow the user to mix and match one of six transceivers with up to one of six different amplifiers, to have the ability at the flick of several switches to key an amplifier with a transceiver, or key both an amplifier and transceiver, with delay by either a hand switch, foot switch, or even computer control.
In this project, I am intergrating several kits from Ham Gadgets by Dale, N0XAS (http://www.hamgadgets.com/). I have limited time to get on the air. I don't have time to design, locate all the parts, etch a board, and then put it all together. IMO Dale's kits are great, and he provides prompt informative help as needed. He even enjoys getting feedback to improve the kits. You should give one of his kits a try sometime.
Other features are also in the works as this project evolves. As I continue to virtually build the interface, I keep thinking of additional features to add to this project.