Create manually-sized gaps along edges of the screen which will not be used for tiling, along with support for toggling gaps on and off.

Note 1: For gaps/space around windows see XMonad.Layout.Spacing.

Note 2: XMonad.Hooks.ManageDocks is the preferred solution for leaving space for your dock-type applications (status bars, toolbars, docks, etc.), since it automatically sets up appropriate gaps, allows them to be toggled, etc. However, this module may still be useful in some situations where the automated approach of ManageDocks does not work; for example, to work with a dock-type application that does not properly set the STRUTS property, or to leave part of the screen blank which is truncated by a projector, and so on.

You can use this module by importing it into your ~/.xmonad/xmonad.hs file:

import XMonad.Layout.Gaps

and applying the gaps modifier to your layouts as follows (for example):

layoutHook = gaps [(U,18), (R,23)] $ Tall 1 (3/100) (1/2) ||| Full  -- leave gaps at the top and right

You can additionally add some keybindings to toggle or modify the gaps, for example:

, ((modm .|. controlMask, xK_g), sendMessage $ ToggleGaps)               -- toggle all gaps
, ((modm .|. controlMask, xK_t), sendMessage $ ToggleGap U)              -- toggle the top gap
, ((modm .|. controlMask, xK_w), sendMessage $ IncGap 5 R)               -- increment the right-hand gap
, ((modm .|. controlMask, xK_q), sendMessage $ DecGap 5 R)               -- decrement the right-hand gap
, ((modm .|. controlMask, xK_r), sendMessage $ ModifyGaps rotateGaps)    -- rotate gaps 90 degrees clockwise
, ((modm .|. controlMask, xK_h), sendMessage $ weakModifyGaps halveHor)  -- halve the left and right-hand gaps
, ((modm .|. controlMask, xK_d), sendMessage $ modifyGap (*2) L)         -- double the left-hand gap
, ((modm .|. controlMask, xK_s), sendMessage $ setGaps [(U,18), (R,23)]) -- reset the GapSpec
, ((modm .|. controlMask, xK_b), sendMessage $ setGap 30 D)              -- set the bottom gap to 30
]
  where rotateGaps gs = zip (map (rotate . fst) gs) (map snd gs)
        rotate U = R
        rotate R = D
        rotate D = L
        rotate L = U
        halveHor d i | d `elem` [L, R] = i `div` 2
                     | otherwise       = i

If you want complete control over all gaps, you could include something like this in your keybindings, assuming in this case you are using mkKeymap or additionalKeysP from XMonad.Util.EZConfig for string keybinding specifications:

++
[ ("M-g " ++ f ++ " " ++ k, sendMessage $ m d)
    | (k, d) <- [("a",L), ("s",D), ("w",U), ("d",R)]
    , (f, m) <- [("v", ToggleGap), ("h", IncGap 10), ("f", DecGap 10)]
]

Given the above keybinding definition, for example, you could type M-g, v, a to toggle the top gap.

To configure gaps differently per-screen, use XMonad.Layout.PerScreen (coming soon).