We all put a great deal of effort in getting to the right place at the right time, take our pictures making sure they are technically correct, download the images to our computers and then completely mess up the colour on an uncalibrated monitor!
Every single monitor, be it a separate screen or a laptop's screen behaves differently. No two are identical. Each one shows a completely different tone to the colours we see on screen. On top of this, we change the brightness on our screens (especially on laptops) depending on the ambient light and then proceed to change levels, curves and saturation settings on our images.
These are then saved as jpegs and sent to the office where someone on a calibrated screen proceeds to try and correct our mistakes and as a result the image becomes degraded.
One of the most important things in image processing is to start by having a calibrated screen. For those who have never tried this, it seems a scary and expensive prospect. Surprisingly, its both easy to do and relatively cheap.
You can pick up a good screen calibrator from around £150 up. My personal calibrator is a Gretag McBeth Eye One Display 2 (now owned by and rebadged X-Rite). This came with its own software which was pretty decent. However, I discovered something called Color Eyes by Integrated Color which gives even better results and supports a host of calibrator pucks. You can download a free trial and compare it to the results you get from the supplied software that came with your system.
I've used this on Apple 30" Cinema Screens, an aluminium iMac (which doesn't calibrate perfectly as its screen is way too bright) and several MacBook Pros and a MacBook Air (which calibrated perfectly).
Go on, invest a little money and get your screens set up properly; you won't regret it!