Many photography "purists" will tell you to that post-production is kind of like cheating (e.g. "take the picture you want to take")...but I find that playing around with Adobe Photoshop can be a real benefit. Little things like just one or two steps of sharpness, saturation of color, cropping, etc. can make big differences in the finished product.
For those of us on a budget, rather than spending $600.00+ on CS4, you can pick up Elements 8 for around $100.00. This includes a photo and video editor and I've had very good luck with it. It's a great package for those of us in the semi-professional realm.
I've been playing with the RAW editor settings (rather then large, medium, or small JPEG) on my Canon Rebel T2i. This gives you much more flexibility with what you can do in post production, but it is much more time consuming.
The only thing I DON'T like about photoshop work in RAW is that you tend to lose some of the quality when you convert it back to JPEG format for e-mails, powerpoint, etc.
I do all my work in manual mode on the camera, no flash. I'd rather trade a slower shutter speed for use of the flash any day....a tripod with remote shutter release is a must for this type of photography.
Keep a good journal for each photo too. This way you can refer back to the things that worked in a particular photo, as well as what didn't work. No more wasting film!! Just battery life...