DirtRag Magazine posted an article on making your own 29er/26er.
This project aims to squeeze a 29″ wheel in the space of a 26″. By replacing a suspension fork with a shorter rigid fork, you’ll be able to utilize the space that the telescopic shock required and replace it with the larger wheel. It’s vital that you keep the bike’s overall axle-to-crown and handlebar height the same as when you started. By keeping these two heights the same, you will see few drawbacks. It’s possible that you will encounter toe overlap (if your frame is small), a higher bottom bracket and/or a head angle change. The closer you stick to your original measurements, the fewer geometry adjustments you’ll see.