Set window sizes to 76% and 24% of desktop size

Left Pane

tell application "Finder"
	set {a, b, c, d} to bounds of window of desktop -- the bounds of the desktop
	tell application "System Events" to tell (process 1 whose frontmost is true)
		set position of window 1 to {a, b}
		set size of window 1 to {((c / 100) * 76), d}
	end tell
end tell

Right Pane

tell application "Finder"
	set {a, b, c, d} to bounds of window of desktop -- the bounds of the desktop
	tell application "System Events" to tell (process 1 whose frontmost is true)
		set position of window 1 to {((c / 100) * 76), b}
		set size of window 1 to {((c / 100) * 24), d}
	end tell
end tell

Useful for keeping the browser on the left and Twitter on the right, for example. Launch using Alfred or similar.