Here are the most commonly used display resolutions and aspect ratios, plus how they're typically used.
1280 x 720 (720p - 16 x 9 or 1.78:1): Great for High Definition Video applications.
1400 x 1050 (SX+ - 4 x 3 or 1.33:1): Predominantly a computer resolution. Also excellent for edge blending as the 4 x 3 aspect ratio maximizes screen height.
1920 X 1080 (1080p - 16 x 9 or 1.78:1): The benchmark for full 1080 high definition displays.
1920 x 1200 (WUXGA - 16 x 10 or 1.6:1): Outstanding for applications where both computer and 1080p sources will be displayed, as well as Video Editing where extra pixels allow for viewing the Operating System’s taskbar without blocking Video.
2048 x 1080 (2K resolution - 1.89:1): Although this aspect ratio doesn't match the native aspect ratio of films which are typically 1.85 or 2.35:1, this format is predominantly used for digital cinema.