old yeast

[spgriffin]

I have a smack pack dated August 2009 I found in my fridge, can I still use it? If so how many days before I brew should I smack it?

[slothrob]

That's getting up there, but there should be viable yeast still.
The rule-of-thumb is to allow 1 day for every month from the date on the pack, so maybe as much as 10 days! If the pack manages to inflate, I'd plan on making a starter before using it, however. Otherwise you're guaranteed to underpitch.

[jawbox]

absolutely positively make a starter before using this one. Like sloth said you're guaranteed to under-pitch