Steam announced today, via their private development forums, that developers will now have the option to run their own sales on their games whenever they so choose. Previously, developers had to go through Valve before they could post a sale or discount on their games in order to best decide when such things should occur.
The sales will last a maximum of two weeks and are easy for developers to set up. Although the functionality is not yet available, it should be coming in the near future.
The main takeaway from this announcement is that there will likely be more Steam sales in the future, so prepare your wallets and your hearts for the days to come.