One of the best ways to draw and keep visitors at your site is with a puzzle. They're fun, challenging, and interactive. When you can customize them, such as using words or images to theme the puzzle, it makes the puzzle relevant, and can even help deliver your message.

Today, I'm going to share my favorite customizable online puzzles. All of these are available free, as well!

Be aware that some may require knowledge of HTML, CSS, Javascript, and/or jQuery to implement on your site. If you can't get these to work on a page with other content, you might try putting it on a page of its own, and including it on your main site via an iframe.

Since touch devices are becoming a larger and larger share of online users, I've gone the extra step of making sure all of these work with the greatest variety of touch devices.

• festisite's Rebus Generator:I figured it was best to start out with a simple static puzzle. To begin, make sure the Rebus button is clicked, and enter your chosen phrase. Select your font, font size, and paper size, and click the Layout Text button. You'll be taken to a page containing your custom rebus, which you can save as a screenshot and post to your website. Challenge your readers to post their answers in your comments!

• Alphametic Puzzles: Another simple puzzle you can include with little trouble on your site are alphametics, which are equations in which each digit is replaced with a letter. The classic example is SEND + MORE = MONEY (Answer: D=7, E=5, M=1, N=6, O=0, R=8, S=9, and Y=2 , so the equation becomes 9567 + 1085 = 10652). This site contains both a puzzle generator and puzzle solver. Once you've worked out a puzzle, you can include on your site with just some simple typing!

• Timed Quiz Generator: Yes, I'm including a shameless plug (Why not?). For those who don't already know, the Timed Quiz Generator lets you create quizzes of the How Many Xs Can You Name in Y Minutes? variety, such as this Dr. Seuss quiz. A tutorial video is included on the same page.

• DIY: linkbait in 5 minutes: If you like the idea of a timed quiz, but prefer more direct control over the program, check out 3n9.org's jQuery library that helps you develop timed quizzes. There are plenty of examples and documentation to help on this page.

• Scrabble Word Builder: This isn't so much a puzzle in and of itself, but an idea for the timed quizzes above. For example, if you run a candle site, challenge your readers to see how many words they can come up with using the letters from the word CANDLE. The timed quiz will take care of the timing and scoring, while the Scrabble Word Builder will provide you with the list of answers you'll need. You may want to limit the answers to a minimum of 3 letters.

• Word Search Generator: Here's another programming free puzzle for your site, an it's an impressive achievement. You start by entering a title and the words for your word search, and then select numerous options, such as grid size, colors, word directions, and more. You can even save your setting and reload them later! Once you actually create the puzzle, all you have to do is view the source, copy it, and save it as an HTML file, ready to upload. Still not impressed? Despite being programmed in 2005, the generated file worked flawlessly on the touch-based mobile devices on which I tested it!

• Word Scramble JavaScript: In this puzzle, you're given a jumbled word, and challenged to unscramble the word by clicking on the letters in their proper order. If you make a mistake, you can click on an included letter to return it to the jumble. Simply view the source code, copy it, and save it as an HTML file, where you can add your own words in the array, and then upload it to your site.

• Mad Libs Word Game: Remember Mad Libs? They're a fun pastime where one person asks for several types of words, and then reads a funny story employing the given words. With this jQuery plug-in, you can engage your visitors with exactly the same type of silliness. Try out the online demo to see this in action for yourself.

• jQuizMe: This jQuery plug-in makes creating simple quizzes on your site very easy. You set up the questions and answers in an array, select a few options, and then your quiz is ready. Not only can you mix types of questions, but you can embed just about anything into the quizzer, including images and video.

Speaking of images, what about customizable puzzles using pictures?

• Memory/Concentration Game: This is the classic game where you start with a large group of hidden images, and you're only allowed to view 2 images at a time. The object is to pair up matching images. As an added bonus, this particular version also lets you reveal a message at the end. Check out the demo. If you can be sure that your site readers are using the latest browsers with HTML5 and CSS3 capabilities, you also might like to check out Branko Jevtic's version and Maykel Loomans' version.

• jqPuzzle: If you've been to the Solving the 15 Puzzle section of the Mental Gym, you've already seen this in action. It makes putting together a custom 15 puzzle almost as easy as using an ordinary image tag. The demo page gives you a great idea of exactly what is possible. Once you've set jqPuzzle up, it's a sure way to make your readers take notice of your site!

• JigZone: JigZone is a jigsaw puzzle site that allows you to upload your own images, and create an impressive array of jigsaw puzzles from them. Besides the usual shape of pieces, they include shapes like bulbs, lizards, USA states, and more! The people behind this site have not only made it possible to embed your custom puzzles on your site, but they've gone the extra mile and made sure that the puzzles are playable on touch-based mobile devices, too!

This is by no means an exhaustive list. Do you have any favorite customizable online puzzles I missed? Let me know about them in the comments!