Congrats! If you get a chance, go to the www.discussfastpitch.com Coaching Softball forum and ask the same thing there. Many travel ball coaches there with a ton of experience.

There's a ton of great books and videos out there (mine are lent out right now and I can't remember exact names/authors.)

I would suggest a few things to maximize the fun and learning:
-No laps: Instead of boring laps, have the girls run relays and races. They won't even realize they are exercising, they'll be having fun, will work harder and get more out of it.
-No lines: Line are inevitable, but try to shorten them by running more stations. All to often, you'll see a coach with a bat and 16 girls lined up waiting for a grounder. The coach will be busy and in his/her mind, the practice is very productive, but finds he/she has to keep reminding the girls in line to pay attention or they'll run laps. The reality is that each girl will get very few turns even though it seems like there's a lot going on. If possible, try no more than 3 girls per station unless it's absolutely necessary.
-Have a plan/theme for each practice.
-No lectures: Kids learn by doing. Explain briefly what you want, show them what you want, then get at it. Stop them when needed to redirect or praise, then get back at it.
-Games: If possible, turn every lesson into a game. Use a progression that demonstrates the basic skill, drill it for a bit, then play a game to put it to use. End with a scrimmage to put it to the ultimate use. Praise it every time you see it.
-Scrimmage often: 5 vs 5 or what ever you have. Get them to see/use the skills taught earlier in practice.
-Keep it fun and active: By doing these things, you'll minimize the opportunities for misbehavior and maximize the fun and learning.

Have fun!

Here's some reading to check out when time allows. I don't necessarily agree with everything said, but take what you like and leave what you don't:
www.girls-softball.com/2005/07/beginner-tips-for-coaching-softball.html
www.girls-softball.com/2008/09/oldnew-school-stretching.html

Your enthusiasm and your effort on looking possible ways to start coaching shows your serious and determined coach. Look for conditioning drills, drills on fielding, offensive and defensive plays, Make sure to know the correct form for each skill and most important, look for great ways to motivate your players.

It is important to know your coaching philosophy so you can have a guide on how you will lead your team.

http://www.softballperformance.com/softball-coaching-tips-line-winning-developing/

Thank you everyone for your responses. I am sorry for my ill timed reply. Life is busy with five kids playing every sport except underwater basketweaving! LOL. I am looking forward to putting my team together for this spring. So far I have been busy choosing parents. Yes, you read it right, PARENTS. I grew up playing competitive sports and I remember oh so well how bad some of the parents were. I plan on building my program around enthusiastic and supportive parents. I am confident that I can teach any kid with a passion for the game how to play. I am super excited about having a fun program for mine and everyone else's kids to enjoy!