UPDATE: If this email on the Steampowered forums is legitimate, it looks as though you have a chance to get a wrench any time you successfully craft any item.
Again, there are still a number of things not yet known. This includes whether or not you should be in a server when attempting this, attempting to craft just engineer items, or otherwise. However, it's a start, assuming this email is legit.
Original:

That is, you can have an authentic Australium Wrench today, if you can craft it. That is also assuming you're one of the lucky 100 able to do so.
The Team Fortress 2 Engineer Update page is NOW LIVE! There are a number of interesting things to find on the page, the most notable being a counter for those who have managed to craft the coveted Australium Wrench for the Engineer. Yes, it is live right now but only a lucky few will be able to get it. 24 people have already gotten the wrench, but the thing is, the methods to obtain the wrench are very vague.
Some believe it can be picked up just randomly as a dropped item. Others feel as though it can only be crafted. Yet there are even more that feel the item is a dropped item but only when crafting while playing as an Engineer. Yeah, so it's a bit confusing at the moment on how to earn it. Then again, if there wasn't some mystery, there wouldn't be much contest to quickly fill up those first 100 slots, right?
Again, there are still a number of things not yet known. This includes whether or not you should be in a server when attempting this, attempting to craft just engineer items, or otherwise. However, it's a start, assuming this email is legit.
Original:

That is, you can have an authentic Australium Wrench today, if you can craft it. That is also assuming you're one of the lucky 100 able to do so.
The Team Fortress 2 Engineer Update page is NOW LIVE! There are a number of interesting things to find on the page, the most notable being a counter for those who have managed to craft the coveted Australium Wrench for the Engineer. Yes, it is live right now but only a lucky few will be able to get it. 24 people have already gotten the wrench, but the thing is, the methods to obtain the wrench are very vague.
Some believe it can be picked up just randomly as a dropped item. Others feel as though it can only be crafted. Yet there are even more that feel the item is a dropped item but only when crafting while playing as an Engineer. Yeah, so it's a bit confusing at the moment on how to earn it. Then again, if there wasn't some mystery, there wouldn't be much contest to quickly fill up those first 100 slots, right?