I have used the protocol that Kris mentions from the UoJ and works very well.
Also, I have used the QIAGEN DNeasy plant mini kit, which also works well (and comes with full protocol). I have managed to get PCR product from a 110 year-old herbarium specimen. The first protocol is better for long term storage (especially when precipitated in iso-propanol) and will probably yield more high molecular weight DNA, so if you are doing AFLPs it's better. But for PCR product, the DNeasy kit will work fine too.
Hint: If you decide to go for the DNEasy, you can reduce the final elution volume at the last step, in order to get more concentrated genomic DNA.
Hope that helps