Why do I meditate? Mainly to improve concentration and decision making - areas one always should try to improve.
Why did I start meditating? I am practicing Chen style TaiChi for a while and I was told again and again, that meditating would help improving my "Chi". TaiChi is also characterized as "movement meditation" and it took a while for me to realize that "standing meditation" would improve that. I heard that Bruce Frantzis is especially good at Chi development and finally got his meditation set. This and the constant reminders of Sifu Tony Wong motivated me to actually start practicing.
After a while, noticed improvements and told a friend. He agreed and pointed me to Vipassana meditation with the hint: "will be good for you". Looking at the site, I realized that this requires more commitment than a few minutes standing. After thinking about it for a while, I went to the 10 day class - also as they stress that it is compatible with any religion - I did not want to be converted.
Well, I am now sticking to it for six months - just taking Saturday off (TaiChi day).
Here are some resources, I found most helpful:
Mindfulness in Plain English - An absolute treasure. Explains techniques and background in detail. There is no better book!
Alexander Technique - You can skip that if you paid attention to your mother's advice "sit straight".
Meditation for Beginners (audio) - I found all audios from Jack Kornfield very helpful and I like his humor. He is very good explaining "eastern thinking" from a western view. His down to earth explanations and examples are very insightful.
Mindsight - From a neuroscience perspective explains the effects of meditation. Starts from latest research on how the brain works and gives many examples that an effective way to improve various brain functions is meditation.
So, just meditate - it's good for you :-)