I am glad that you contacted me about getting started in robotics. It is a great hobby to get started in. I am sure you will find it full of interesting new things to learn. How to get started is a very common question I answer every day. I hope you don't mind, but I have written down answers to the most basic of questions on this page. I don't mind answering questions, so feel free to ask after you check out the information I have provided here. This is my attempt to provide you with good up to date information about starting up.
The Internet is full of great information about getting started. There are also several good books available. My first suggestion is to check out The Basics - Basic Information, which is a column I wrote about getting started. To re-iterate the information on that page: Get the Mobile Robots book. It is a great investment if you plan to do anything in robotics. It will cover in good detail many of the things you need to know to get started. You also might be interested in checking out The Encoder Front Page. We try to provide information that is useful to everyone. Check out some of the Basics columns. Robotics FAQ is another great place to find a large amount of good information such as suppliers, clubs, and other information.
Many cities across the USA, and indeed through out the world, have really great robotics clubs. Check out some of the listings on the internet, such as Robotics FAQ to find a club in your area. You also might try doing a search for the keywords 'Robotics Hobby Personal <your city>'. You may be surprised to find there is a club meeting right down the street! If you live in the Seattle area, check out information about Our Regular Meetings.
Many people start out with very grand plans for their robots. The robots are designed to be complex, highly intelligent, and extremely useful. Unfortunately, these robots also never work! I encourage you to take small steps along the way. Building a robot is not simple, but then again it really isn't that difficult. It is somewhere in the middle. Taking small steps increases your chances for success. As a first move, I suggest making your robot move in a straight line. Check out Classic Encoder - A KISS for You for some of my philosophy on the subject.