The DIY Audio forum’s photo gallery is rich with hundreds of amazing projects the DIY audio community has built over the years. I could repost and talk about every single one of them but I really try to avoid it. While browsing I came across the following build and for some reason it stood out from the crowd. The wooden enclosure is a nice departure from the typical aluminum and stainless steel boxes that you typically see.
Flickr user Equaliser (Steve Woodward) has a nice pic of his DIY Polivoks style filter posted. The kit is available through Papareil Synth Labs and on their site you’ll find some good historical information and documentation of its workings. Here’s a shot of the schematic (click for link to original .pdf).
Steve has some great audio clips of the filter in full effect here