Mike Bond, Strength and Conditioning Coordinator at the USSA Center of Excellence presents a great progression of strength and conditioning exercises well suited for traveling on the road or doing at home with little or no equipment. No need for a gym pass!
Bond strongly recommends you do these exercises in the order presented below. Print this out so you have a copy you can follow. The video of how to properly perform the exercises is at the bottom.
You can search Google for mini-bands, or here's a link to buy "Synergee Mini Bands" on Amazon.com (they have glowing reviews). They are very inexpensive.