Here is a layout for a very cool compressor. It's a DIY offering by HEXE Guitar Electronics and a original design based around the TDA7052A chip. Here is a demo-video by the creator

Another great DIY offering from Björn Juhl of BJFE Electronics.
This is a simple clean booster that can boost alot.

This is a very cool and versatile tremolo by Electric Druid. The signal path is taken from the Tremulus Lune, but the LFO is replaced with a digital chip with tons of features: Tap Tempo, 8 different waveshapes (even a random shape!) and a multiplier function. If you are new to digital chips that require code, read more in my Guitar to MIDI post. Have a look at my finished build here.

Read more about this project and download the HEX code or buy the PCB/pre-programmed chip-kit here: http://www.electricdruid.net/index.php?page=projects.taplfo

I also drew up this layout with only the LFO, Figured it might come in handy. For example to modulate the speed of a delay to create some pitchbend/chorusy effects... Hmmm, wonder how that random waveshape will sound. :o) I have not built this one yet, but it should be ok. Hook up A and B to any pot you want to modulate/replace. Use a regular LED and wrap it in heatshrink or tape with the LDR or use a vactrol. I used a  VTL5C3 vactrol in my build.

Here's a very cool synthy sounding octave down / up invented by Slacker (the creator of The Echobase). Original thread here. I included the Octave up addon from the schematic aswell. I had to use shitloads of cuts and links in this layout, but at least I got it into a good size. :)

I did have problems getting this one to work/track properly. Only the low E and A strings tracked and I had to hit the strings hard. Here is what I did... Probably not the best solution lol, but for now it's good enough until I have more time to try out other things. If you want to build it 1:1 with the schematic, just omit the 47K resistor. Here's a short soundclip of the circuit/layout (with my fix):

I'm using humbuckers, neck pickup, mix at 50%, Octave up maxed and 2nd octave down selected.

A very cool sounding ring modulator by Carlin. Have a look at my completed build here. I put a 4.7nF cap between vol lug 1 and 3 (ringmod output - ground) on my build to tame some of the treble a bit.

UPDATE:
Now updated with a oscillator daughterboard to make it much more useful. :)

On its own the Carlin Ringmod sounds kinda like a starved octave fuzz. To achieve the typical ringmod effect you have to connect an external tone-generator. Sadly not without the classic ringmod problem - carrier bleedthough (alot in this case). But my daughterboard takes care of that issue.

My idea was to put the tone generator in the box with a in/out switch insted of having two inputs like the original. I also wanted the signal to gate when not playing. This is what I came up with and it's working great.

it's a VCO (voltage controlled oscillator) controlled by a VCA (voltage controlled amplifier), which means that the VCA is triggered by the guitar signal and turns off the VCO when not playing - no more carrier bleedthough. :) The idea came from the Penfold Fuzz Unit circuit thanks to Moosapotamus video and the oscillator is taken from the LM13700 datasheet, modified for single supply and useful freqency range.

I just realized I forgot to post my HM-2 layout that I did a year ago.

The "Mini-Muff" by Jack Orman is basically a Big Muff with two of the gainstages removed. It doesn't sound much like a Muff, but makes a surprisingly good overdrive/distortion.

Here's something fun that I found at diystompboxes.com (original thread here).

It's a little circuit that converts your guitarsignal into MIDI language, so you can use your guitar with your favourite synths. :) It's monophonic, so it's not good for chords but works ok for single notes, leads, basses ect.

It requires a specific PIC chip and PIC programmer hardware (such as pickit2), software, and code (downloads at the bottom of the post) to be written onto the chip, so it's a bit harder to do then your regular stompbox. More info below.

This is what you will need:

• The PIC16F88 chip. It's an older 8-bit chip, but still easy to find (try ebay). The code is written for the chip so other PICs with not work.
  
• The hardware required is either pickit2 or pickit3. I borrowed a pickit2 from a friend, but you can buy them here. Pickit is basically a interface that connects to your computer with USB and lets you read/write/erase programs to the PIC chip. Keep in mind though that the chip-socket may not have the same pinout as the chip. I used a breadboard to jumper the connections, as shown here.
• There are alot of choices for the software (all free). I used PICkit 2 v2.60, but MPlab and PICgm Programmer are also good,
  
• Code! Download the required code below. Only one of them is needed. Try the second one if you are having trouble writing the code to the chip with pickit2.
  

Here's a good circuit if you want to avoid those clunky and expensive 3PDT switches and use a soft-touch momentary SPDT footswitch insted, or something else, like a push button switch.

One could argue that this one isn't really suitable for vero (tons of links...) or worth the effort, but I think it's nice for those extra special builds and it's also much cheaper than using relays. It does take a bit of space, but it can fit in a 1590B (depending on the size of the effect circuit).

Another cool effect by Robert Penfold. I could not find any info on this one so I made a layout out of pure curiosity. I was expecting a ring mod, but it's actually a cool metallic sounding octave fuzz/distortion with a fairly strong octave up and a weird stutter/tremolo mode (!) depending on how the Bias pot is set.

The only problem with this circuit is that it uses a LM565 chip which is obsolete and can be hard to find/expensive. I didn't discover that until the layout was finished (doh..) so I had to pay around 10€ for five chips from ebay.

Note that the trimmer has a very small sweetspot for the effect to work at all.