You can associate your email address to a Google Account without signing up for Gmail. This is really useful for a few things, it'll let you access Google Docs and other Google Services.
(Note: This does not in any way affect how you send/receive email.)
Step 1: Head over to https://accounts.google.com/
Step 2: Choose Create an account
Step 3: Select Use my current email address instead
Follow the prompts and you're done! Welcome to a new world of possibilities (more realistically, you really just have easier access to Google stuff).