According to Matt Cutts, linkbait is anything "interesting enough to catch people's attention." Of course, the best linkbait doesn't just catch it but keep it. These five sites are worth re-visiting; here's why they work.
1. Lifehacker 
Consistently named to lists of the web's best, Lifehacker (part of the Gawker Media family) is a blog of "tips and downloads for getting things done."
Why This Works: Far from a short-lived linkbait gimmick, this is a legitimately useful website full of life improvement tips (including time management, organization, and smart repurposing) geared toward the tech-geek type. Recent popular topics include "Turn an Older iPhone Into a Prepaid Voice and Data Unit," "Rename Files Fast with the Tab Key," and "IKEA Jerker Do-It-Yourself Treadmill Desk." Because clever how-to content is linkbait gold, and because this site has an active teach-savvy community, almost every post is ready-made linkbait! Lifehacker is a great model for sustainable linkbait that really adds value (as opposed to being merely a fun a waste of time).
Ships That Pass is "a collection of fake, imagined, and literary missed connections posted to Craigslist and then re-posted here with real and actual responses."
Why this works: The Missed Connections  section of Craigslist is an awesome way to waste time in and of itself, and there's always room for good variations on a good thing. (For example, notice how many desserts are improved by adding ice cream or peanut butter.) When brainstorming linkbait, you don't always have to start completely from scratch; you can bootstrap by building a site or a tool that riffs on another site that's already established and popular. (Along these same lines, see the Firefox add-on that allows you to "dislike" something on Facebook .)
"Need catchy blog post ideas?" Enter a subject and the Linkbait Generator provides a list of absurd and hilarious titles that just might work.
Why this works: This tool that helps you brainstorm linkbait is great linkbait itself. Making it easier for people to do the things they want or need to do is a pretty failsafe way to get attention. Coming up with the concept is Step 1 of writing a great blog post. Other steps include keyword research (linkbait: keyword tools) and adding images (linkbait: a tool to help you find appropriate pictures for your posts). What other tasks or processes can you make easier for people?
4. Wordle 
According to the site, "Wordle is a toy for generating 'word clouds' from text that you provide. The clouds give greater prominence to words that appear more frequently in the source text." You can then edit your clouds with different fonts, colors, and layouts.
Why This Works: Here's another one that's been around for a while but hasn't died yet. Why? Because people still think it's nifty, I guess. Unlike the Linkbait Generator, Wordle fulfills a need people didn't know they had. It's just entertaining to see the words you use most frequently on your blog or in a document, and it's useful to readers too, since it reveals your most common topics. This tool works because they found a way to present information—information that's fairly easy to extract—in an attractive and interesting way. Often, a little design mojo is just as valuable as coding pyrotechnics.
5. Basenotes 
Basenotes is a directory of information about 13,000+ fragrances, including member-submitted reviews and a forum. It's a great resource for perfume lovers who like to do a little research before laying out for a new FB (that's perfume code for "full bottle"), and bloggers and social media users often link back to its pages.
Why This Works: This is just one example of a focused, niche review site. Most hobbyists are also consumerists—you need supplies of one kind or another to fuel your hobby—so they're frequently looking for up-to-date reviews from likeminded consumers they can trust. Do you have a hobby or extensive knowledge in a certain product niche? Photography (cameras and film)? Fishing (rods, tackle, flies, vests, wading boots)? Is there already a dedicated review site for those products? Can you make a better one? BONUS: Review sites are a great way to leverage user-generated content (that means less work for you).