DIY Modular Synthesizer
Here's the most recent picture of my Analog Modular Synthesizer as of Sept 2008.

Every module has been built over the past two years.
This is a rough 'Noodle' I recorder recently - It's all hands off - no keyboard, no knob twiddling.
Noodle091808
I just built the upper right hand 2 rows of cab - Just got to catch up with my backlog to fill it.
Here's how I got started building - and a few shots of various projects
I had been looking for a Moog Micro synthesizer for several years. My interest in a synth was primarily to learn about analog synthesis. With my tech background I expected I could find one that needed repair, fix it up and then sell it when I learned what I wanted to learn from it.
I finally found one for a couple hundred dollars on E-bay and purchased it. It was a mess – but some power supply work, changing a few pots, and a good cleaning gave me a useable Moog. It was fun – but I decided it would be great to have a sequencer to use with the Moog.
A Google search for "Analog Sequencer" pointed me to several sites and I stumbled across Ray Wilson’s "Music from Outer Space". Ray’s site provided very nice circuit boards and instructions for building a nice 16 step sequencer, among other projects for building an entire analog modular synthesizer one module at a time.

I ordered up the Sequencer boards and parts in late October of 2006 – and began to follow links into the world of SDIY. By the time I had completed the sequencer I had remembered how much I used to enjoy building electronic circuits as a kid. And I wanted to make more.
In November of 2006 I ordered a VCO, VCF, VCA, and ADSR PC board from MFOS.
In December 2006 I followed with another VCO, ADSR, LFO, VCF and Noise Cornucopia from MFOS. More boards followed in late December 2006, and I also began to build other circuits I found on the Internet on perfboard.
The winter was spent building, mounting and learning to use the various modules. My initial case was in a four unit high rack with panels for each module – something like a Frac rack. As I continued to build I decided I wanted a more traditional look for the synth, and decided on a Moog Modular format in a wood case. Using wood I had on hand from an old church organ I made a couple racks that would hold 12 of my modules each.

I scrounged some 1/8 inch aluminum from a nearby metal fabricator shop and cut my panels to size using a table saw.
In March of 2007 I found the Electro-Music.com website. This website has an great community of Synth builders and designers - and enough unique circuits and PC board offerings to keep me busy building.
This is the 2 row Cab on the Lower Right.

The electronics for this cabinet were built in Winter of 2007-08 with the exception of the Pattern Generator and Synthacon VCF.
The MFOS VCO's & VCA's, Thomas Henry QFQ and Mankato VCF and Fonitronic Attenuverting Mixer were made with purchased PCB's - the rest were built from schematics shared on electro-music and around the web.
Top Row Modules
1in/4 out CV Dist & 3 Passive Attenuators (Normalled to CV Dist), 2 MFOS VCO, Thomas Henry Mankato VCF, 2 MFOS Dual VCA, Polyfusion 2044 copy (Env Follower/Gate Extractor), Fonitronic Attenuverting Mixer, Thomas Henry VC QFG, Ian Fritz Driven Double Well Chaos, 4 in/2 out Mono Mixer, repackaged RatShack Reverb.
Bottom Row
EFM VCO-VCA, Grant Richter CV Twister-Wave Warper, Blacet Freq Divider copy, Ian Fritz Dual AD/AR Gen, Synthacon VCF copy, 3 Pulse Dividers, 4*4 Mults, 3 MFOS Simple LFO, Synth X Random Gate/Uncertainty Module copy, Dual Bugbrand Pattern Gen with Triggers, AND/OR/Inverter Logic, CGS Gated Comparitor, 2 *4 Mults
The module panels are 8.5 by 2.25 inches by 1/8 inch aluminum. Labeling is clear Dymo.
Mahogany probably isn't the best choice for durability - it gets 'dinged' pretty easy - but it's easy to work with, inexpensive and I like the look. Two 4 foot by 7 inch by 1 inch pieces of mahogany were used for the frame, and a 1 inch by 3 inch piece for the center divider.