PEG, poly ethylene glycol (sp?), a water soluble stabilizer that you submerge the piece of wood in and the chemical (apparently non-toxic btw) will displace the water (it is basically a wax) over several+ days, the wood remains perfectly workable, it will prevent splitting and degradation etc.. It is used to preserve archaeological (ancient) woods, like ships for example that have been submerged for 2000 years. It is inexpensive, readily available, and very easy to use, there is a lot of info on it, go Google M8!
Barring that there have been several methods discussed here (for larger slabs) of slow drying/curing, packing in straw or sand in a cool dry place are a couple, lots of info on that too espcially if you have a library nearby, but the gist is to do it slowly and sometimes endsealing is a good option to slow the process down but it really depends on the size of the piece I think. My 0.02$ worth fer da afternoon.
Hope that helps man!
Serge