With an estimated 75 million people sending over 1.5 billion messages or "tweets" a month (and growing!), Twitter is an increasingly important way to connect with your customers and prospects – one you can't afford to ignore. Not sure what Twitter is? Read here.

Why not promote your business using one of the Twitter advertising services that have sprung up in the last 18 months or so. Here's a list of the 15 best Twitter advertising services for you to consider (so far!)

We've ranked them based on our editorial review, monthly visitors (estimated by Compete), and Google page rank (a key factor in determining ranking in search results… the higher the number the better). Full disclosure: we haven't tried them yet but will soon. Stay tuned for updates!

You'll also notice there are different pricing models to choose from. Try them all… and decide what works best for you. The good news? Most of these Twitter advertising services only cost $10 to $20 to test. So what are you (and we) waiting for!

Looking for even more ways to take advantage of Twitter with your marketing dollars?

There are lots of Twitter related sites such as TweetMeme and CheapTweet that sell advertising. How about a tweet press release service? Check out Muck Rack for your one-sentence news release!

And there's plenty more to come as Twitter advertising is just getting started.

Btw, don't forget to follow us on Twitter. = )