Have you ever wanted to just draw a simple dashed or dotted line in Photoshop? This should be simple, right? Well, it's not too complicated if you know where to look. But I'll admit, it is a little round-about.
1) Select either the Pencil or Brush tool
2) Select the brush size you want to use for your dotted line (Hard-edged brushes work best). If you want a dotted line, use a round brush, if you want a dashed line, you will need to load the Square Brushes library. To do this, click on the brush size icon in the options bar, then click on the fly-out menu (circle with an arrow icon) and select Square Brushes.
3) Access the Brushes palette (it lives in the palette well by default), click on the 'Brush Tip Shape' to display those settings and change the Spacing setting to a high value (200 or more).
4) Draw on your canvas while holding down the Shift key, which allows you to draw straight lines.
(Tip: Click once to set down the start point of your line, move your mouse to where you want the end point to be, hold down the Shift key and click again. This works with any tool that uses brushes: Healing, Clone, Burn, etc.). If you want longer dashed lines, you'll need to create your own custom brush.