When I save a document, can I enter the location with path input?
Basically, just start typing the path you want to use in the Save As: field. The Go to Folder dialog will appear when you type / or ~ and let you type your path. Type your path and press return. You can include the filename at the end of the path and it will update the name automatically.
You can also access the Go to Folder dialog manually using  &#x2318;-&#x21E7;-G.

You can't create a new folder by typing the path, but you can use a keyboard shortcut to create the folder. Use Go to Folder to get as deep as you can into existing folders, then type &#x2318;-&#x21E7;-N. Type the name of the folder and press enter.

The field with the filename will selected, so you can just type your name and press return.



This question has inspired a post on the Ask Different Blog that contains the answer, as well as other tips for working with open/save dialogs.