If you are an "at-home" type stretcher, and are interested in yoga, Richard Hittleman's "28-day yoga plan" is excellent, and the program will ensure you don't injure yourself by over-doing it. You can find the paperback in most used bookstores for under $5
I stretch in the morning, but have heard that stretching before exercise can cause injury. I had been doing morning yoga for 5 years before I heard that.
Pilates is also good, but a bit more $$.
My $.02
-Moses