What better on a Saturday morning than a tip to make your life easier?
I bet you didn't know that iTunes creates a folder that will automatically import then delete anything thats put in it?
I know! There is.
So where can you find this your asking?
Well, if you look into your iTunes folder and dig deeper, you'll find it nestling between the folders that iTunes now uses to organise different media types. Back in the day when it just handled, well, er, Tunes it would simply have one folder, but now that iTunes will handle a range of media such as Books, TV Shows and Apps it has split them up into folders. Amongst this, as you'll see, is the 'Automatically add to iTunes' folder:

Auto: Any iTunes compatible file you drag in here will be ingested
So give it a go. Its pretty instant. What's best of all is it wont leave duplicates of MP3's or M4A's all over your hard drive, as once imported and copied to your iTunes library it deletes the original in the folder.
You can get really clever though by using Aliases. Perhaps you may always download MP3's of a mix to your Downloads folder, or you share recordings with a friend on Dropbox?
Create an Alias of the 'Automatically Add to iTunes' folder by right clicking sorry, Windows speak there, by CMD + clicking on the Folder and selecting 'Create Alias':

Alias: The Finder equivalent of 'Create Shortcut'
This will create an alias of the folder. Why an Alias? Well if you simply made a copy of the folder then it will loose its Automatic magic. An alias therefore creates what is effectively a shortcut to that folder.
You can then move this Alias to say your Downloads folder or Dropbox folder , meaning you have a really easy way to import now to iTunes. As soon as your MP3 has downloaded, drag and drop within the same Finder window and boom! It's ingested to iTunes.
If your getting really clever you could set your Video or Audio conversion apps to always output to this folder, making it even more seamless.