I always get my LME in bulk from my LHBS. Many of the internet shops sell bull LME as well. The stuff that comes in the cans can be pretty elderly before it even gets to the shop, let alone when it finally gets sold and delivered to you. Freshness is the most important thing when it comes to LME. Stale extract puts your beer at a disadvantage before you even get started.
"Science + beer = good!"