These days, most people turn to the internet for information, resources, entertainment and networking. I believe that some sort of web presence - be it a website, a blog or some combination of the two - is essential.
If you want to license your art and will be doing your own marketing, contacting manufacturers directly, you need to have somewhere to direct them online to see your work. Everyone is busy so the easier you make it for someone to get a snapshot of who you are and what you do, the better your chances of making a connection that will turn into business.

You can send samples of your work as jpegs attached to an email, but some sort of permanent web real estate is ideal. If you aren't online, you need to decide between a traditional website or a blog as a starting place.
The fastest, easiest and often free way to get online is to create a blog. There are many blog sites that offer free blogs, complete with templates, and you can be online within minutes. If you want more control over the entire look and feel of your blog, you might need to get help from a web designer and it could take a little longer.

If you aren't familiar with what a blog is - I believe it started as an online journal of sorts. Some people have personal blogs where they write about their day, observations on life and general musings. There are news blogs, self-help blogs, networking blogs and more. Pick a topic and I bet you can find more than one blog out there.
If you are starting out and want to keep your costs down, start with a blog. Create a blog whose purpose is to show your work and give basic information about you. This isn't the place to show off pictures of your new puppy (create a personal blog for that) but a place to promote your business.

This is not to say that websites are expensive. You don't need to have a high-tech site with lots of moving parts and you don't need to spend thousands of dollars to have someone create and maintain your site if you don't want to. Like blogs, there are a lot of companies that offer turn-key options for websites as well.
To get a site going, you first need to register a domain name. Ideally, it should be the name of your business, or your name, and I STRONGLY believe you should get a ".com" name for your main site. Register .net and others if you like, but people search .com first. If you choose a name and register ".net" because ".com" is already taken, just be aware that you will probably drive traffic to the ".com" site. I will, however, give you some guidelines about what to include - either on your website or your blog. These are some basics to get you started - let you and your art shine through!

1. Your business name & logo
2. Contact information. You will be amazed at how many people forget to put an "email me" link on their website because they get so involved in the content.
3. Samples of your art. Put enough images that a manufacturer can get a feel for your work and decide if it might be a fit for them or not. Don't put everything you have online however, as sad as it is, there are people who might copy or steal art online so keep a balance between showing enough and tempting fate.
4. Information about you. You are not only selling your art but also yourself. You are a person, trying to connect with a person who works for a manufacturer, or a person who is an agent-- perhaps your future agent. Give them an idea of who you are. Have you been painting since you were 3? Why do you choose the topics you choose? Do you have formal art training or did you learn at your grandmother's side? You get the idea!
5. Information about your business. If you have licensed some of your work, show samples or talk about it. If you have your own card line that you sell in local stores, talk about that and how the sales are. Any details that show that retailers and consumers already like and buy things with your art on them is a good thing. Get online if you aren't already and if you are, take a few minutes to look at your website and/or blog and make sure it represents you, your art and your business.