The home designer doesn't have to spend buckets of money on design software, a lot of free software is available. From EE Times, we learn that Allied Electronics and RS Components have teamed to produce a suite of free software called DesignSpark. Who? Allied is a US company with a history stretching back to the early days of radio - they used to be Allied Radio. RS Components is better known in Europe.
Somewhere in the clouds, we have a company known as Electrocomponents PLC. This company boasts more than $2 billion of annual revenue, more than 1 million customers, and operations in more than 30 countries. The two main brands in the Electrocomponents empire are Allied Electronics and RS Components.For building one or two of a design (yours or from someone else) or for experimenting, hand point-to-point wiring or dead-bugging will get you there. (The name comes from how components can resemble dead bugs when they're mounted on their backs with their leads sticking up in the air). As the components get smaller, like today's surface mount parts, or as the circuit gets faster, like a fast computer board or radio, there's nothing like a printed circuit board (PCB) to help get predictable and consistent performance. The DesignSpark suite includes a PCB design program with full-professional capabilities, DesignSpark PCB. They describe it this way:
DesignSpark PCB is offered completely Free of Charge and fully featured. This is not a cut down version of an expensive product or one with a time limitation on license. (There are no intentional restrictions on designs). There are unlimited schematic sheets per project, up to 1m squared of board size and no limits on layers, which allow you to get your creativity flowing without restraints. DesignSpark PCB circuit design software can be used for schematic capture, PCB board design & layout, generating impressive 3D View to visualise your design in real time, and generating manufacturing files.There are companies like PCB123 (Sunstone Circuits) who specialize in small runs of PCB production. They give away design software a bit more limited than DesignSparkPCB, you design the board in this software, send them the program's output, and they'll provide you boards with very quick delivery. The problem with these guys is that you're limited to using just them to produce the PCB.
Circuit simulation software that can help you be sure a circuit you designed will work is available, too. DesignSpark links to a program called "GreenPoint" from ON Semiconductor, which looks to be a SPICE-type simulator (Sidenote: SPICE, Simulation Program with Integrated Circuit Emphasis, is a program developed at UC Berkeley in early days of integrated circuits. It is pretty much the standard way of analyzing circuits in great detail, especially for lower frequency analog electronics.) I use LTSpice, from Linear Technology, another free program. There are others. TINA from Texas Instruments, and MultiSIM from Analog Devices. Here's a useful summary.
You're going to need a housing or box for whatever you build, and DesignSpark has you covered with a 3D modeling tool DesignSpark Mechanical. And I'd be short changing you if I didn't mention Google SketchUp. Never touched it, know almost nothing about it, but I know woodworkers are finding it useful.