Apple - Do any window managers allow me to snap windows to the sides of the display?

SizeUp is exactly what you need:

SizeUp allows you to quickly position a window to fill exactly half the screen (splitscreen), a quarter of the screen (quadrant), full screen, or centered via the menu bar or configurable system-wide shortcuts (hotkeys). Similar to "tiled windows" functionality available on other operating systems.

Divvy

Divvy is a little menubar app that allows you to automatically resize any active window. Divviy virtually divides your screen into a 6x6 grid. When invoked, Divvy brings up a little HUD in the middle of the screen with this 6x6 grid. Depending on what part of your screen you want to resize your active window, just drag and select those squares on the HUD and the window does the rest. It’s that simple.

After testing SizeUp and Breeze, I've decided that Breeze fits my needs the best. Both allow you to position windows on the left, right, or Fullscreen. The feature that sold it for me was setting a default size & position for an application and assigning it a shortcut key.