I use active dry yeast and store it in the fridge...if I'm not mistaken, this is the same as baker's yeast It is important to keep it dry (the temp shouldn't exceed 80ºF) so an air-tight seal or a good fitting tupperware can work. As long as the tem doesn't exceed 80F the pantry can be alright though I lean toward the fridge. Just keep the humidty out.
Freezing does not work according to John LeVasseur :
"It is worth noting that there is disagreement among the yeast companies as to whether or not active dry and instant active dry yeast should be frozen, and if in doing so the shelf life of the yeast is prolonged. The most convincing argument against freezing is that under normal conditions, there are temperature fluctuations in freezer units caused both by repeated opening and closing of the freezer door and, in contemporary freezer models, by the self-defrosting (freeze and thaw) cycle. These temperature fluctuations can cause damage to the yeast cell structure.
One topic upon which there is agreement is that if active dry or instant active dry yeast has been refrigerated, and is going to be rehydrated in lukewarm water, it is best to allow the portion of yeast to be used to come to room temperature prior to blending it with the lukewarm water. Otherwise, temperature shock might damage the yeast cells."