Gary Shutt shows how to get the low 7 string sound on a normal 6 string, using B standard tuning. What you need to do is get yourself some really thick and heavy gage string like 13 through 56 or a 7 string set and just not use the 9. Once you have your strings on, you tune everything down to perfect fourths. Going from the lowest (bass) to highest strings you will have: B-E-A-D-G-B.
So both of your outer strings will be B's and they will have the same lowness and chunkiness as a 7 string without the high E string. You can play your normal 6 string chords this way.
This is a step-by-step guide on instructables.com shows you how to make a skatar (a guitar skateboard). Instructables contributor ntagn33 describes how he took a Squier Jagmaster and mounted skateboard trucks on the back. Then he added griptape to the front, making it a fully functional guitar-skateboard.
This is a step-by-step guide to scalloping your fretboard. Scalloping is the removal of wood between the frets (usually from fret 14 upwards). Some players, like Yngwie Malmsteen, favour a scalloped fretboard as it is supposed to make it easier to play fast.
The tools needed are: a round file and sandpaper for wood removal and a Dremel for polishing.
This instructable shows how to make a folding guitar. The technique of folding the neck using a hinge to the body end of the neck is not new, but this guide shows a DIY version. This guide has some interesting ideas, but I would say its still in the development stage: I can't see a mechanism to lock the unfolded neck in place. There is also a strange cylinder mechanism on the back of the neck that coils up the strings when the neck is folded, but it looks like it would get in the way when you are trying to play the guitar.
Drop B tuning is an alternate tuning for a six string guitar used by metal guitarists to achieve a deep and powerful sound. To get this low 7 string sound on a normal 6 string you need to do get yourself some really thick and heavy gage string like 13 through 56 or a 7 string set and just not use the 9.
If you like tinkering with electronics this page on home-wrecker.com describes some modifications to the vox v87 wah wah pedal. By changing some of the components, you can tweak the range and limits of the wah effect.
This project shows how a guy modified a cheap yard-sale guitar into a travel guitar. He sawed off most of the body and the head-stock and put the machine heads behind the bridge. Unfortunately the finished product does not balance properly like a Steinberger , the neck falls down if you let go of it. Maybe some weight could be added to the body?