Windows Split Desktop Utility

I'm a big fan of WinSplit Revolution. It's got some great default settings for window locations/sizes, but is also fully customizable. I'm using it for coding on dual monitors, but have also used it on a single monitor and it works great for that too.

MaxTo - MaxTo is a program that lets you maximize windows to different parts of your monitor. Ideal for programmers, graphic designers and anyone else who needs to have many windows visible at once.

Works very stable.

Are you thinking about something like Windows Snap?

I don't have a program to do that but DisplayFusion does include options to snap windows to the sides and corners of the monitor (and some clever middle-click/drag options to switch maximised windows to another monitor).

I use a free utility called GridMove with success. It allows you to position and size windows to sections/areas of your monitors. And the templates that it uses are customizable.

I use a grid created by user 'excogitation' on the forums (look for the download links at the bottom of his post)

It is only a sample program for a .NET library..., but I like NeatKeys for resizing windows so that they align to each other (for presentations etc.). There are several modes (one with presets like Winsplit Revolution, one where you draw lines and then assign your windows to the existing rectangles, and one where you can just save current sizes and attach shortcuts to them). Most features can be used both by keyboard and by mouse.