If you know what keyword research is, then you probably know the basics of what you're supposed to do with it – namely, use it for on-page optimization (in your title tags and the text of your web pages) and for PPC (bidding on those keywords and using them in your ads).

But what else can you do with those keywords? Once you've taken the time to aggregate a keyword list, you might as well leverage those keywords in as many other ways as possible for marketing purposes.

Here are five more things you can do with those keywords, beyond the SEO and PPC basics, to get additional marketing leverage from them.

1. Email Subject Lines

The whole point of doing keyword research is to find the terms that speak to your client base and people you want to add to your client base. So even when searchability isn't a concern, why wouldn't you employ those same terms? If they work for SEO, there's a good chance they'll work in your newsletters and email blasts. Try incorporating your keywords into subject lines to increase open rate, and use them in the copy to boost clicks and conversions.

2. Product Brand Names

Rather than trying to come up with something really clever and catchy, like "Swiffer" or "Zubbles," you can just use keywords in your brand names when you develop new products. It's kind of boring, yes, but it's great way to ensure that your product names are search-friendly and to get built-in anchor text when you receive unsolicited links. This was what we were thinking when we named our free keyword tool "The Free Keyword Tool" – the name gave us the opportunity to rank in searches even when the searcher didn't yet know our tool existed – in other words, the search query "free keyword tool" may or may not be branded. Either way, we can grab that traffic. So think about branding your product with a keyword phrase that describes its functionality – for example, "Website Builder" or "Pool Vacuum."

3. Your Blog Name

Your blog's name is another spot where you can use keywords to your advantage, merging SEO into your blog's brand. If you're planning to launch a blog, think about the keywords that a potential reader might use when looking for information on the topics you plan to cover. Geordie Carswell, Giovanna Villanueava, and Aaron Wall's PPC Blog is a great example of this (it ranks #1 in my browser for that query). This same principle could work for any kind of blog with a strong topical focus (Easy Vegan Baking, DIY Gardening Daily, etc.).

4. In Your Bio for Guest Posts

This seems like a no-brainer, at least for the obsessive link builder, but many marketers miss the opportunity to use keywords in their bio when doing guest blog posts and other forms of article marketing. There are ways to get an anchor text link into your bio without looking super-spammy. For example, instead of a bio like this:

Betty Crocker works at Acme Marketing Co. and maintains the blog The Seasoned Chef. She lives in Modesto.

You could write a bio like this:

Betty Crocker is a marketing consultant in Modesto. In her free time, she blogs about vegetarian cooking on a budget. Follow Betty on Twitter.

5. Twitter Accounts

It's important for your primary Twitter account to be branded. So if your company is called ABC Inc., your Twitter name should be @ABC or @ABCInc. But consider creating additional Twitter accounts using keywords relevant to your business. For example, if your company is in the travel industry, you could start an account called @TravelTips that shares original travel tips on a regular basis, retweets other travel tips and answers questions. This could be affiliated with your main brand account and link back to your site. This is a way to attract visitors who are at a more informational stage of the buying cycle; if they have a positive experience with this helpful social presence, they may later come to you when they want to purchase travel services.

These five ideas are just a starting point. What else can you do with your keywords?