In any Finder window or Open/Save dialog, you can hit ⌘⇧G (just '/' also works in Open/Save) to get a location bar from which you can directly type in the directory to go to. It even supports ~ for home and tab completion.
The Open/Save dialog has several other useful shortcuts:
⌘ R - Reveals the selected item in a new Finder window.
⌘ I - Info window shows for the selected item.
⌘ ⇧ > - Shows/Hides hidden files in the dialog
⌘ F - cursor jumps to the Find text field
/ or ~ - Opens a Go To Folder dialogue.
⌘ D or ⌘ ⇧ D - selects the ~/Desktop folder as a destination
⌘ ⌥ L - selects ~/Downloads folder as a destination
⌘ ⇧ O - selects ~/Documents folder as a destination
⌘ ⌥ S - Shows/Hides sidebar
⌘ . or esc - Cancels and closes the dialog window
