Want to know what’s happening anywhere in the world rightnow? Twitter is where it’s at. Want to know what’s beenhappening over time and in the context of other events? That’s where it gets a little more complicated.

Fortunately, Twitter’s open API means that Trending Topicsaren’t just for the network’s homepage. Developers can tap in and display data about popular tweets, terms, and URLs that allow us to compare and track trends over time and find out what’s hot or newsworthy beyond that simple top ten list.

Whether you’re tracking your brand, optimizing your content, or just plain curious about the way information is virally shared, you’ll want to check out these five web-based tools for keeping tabs on Twitter trends.

1. Trendistic

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Trendistic (formerly Twist) is a go-to utility for getting granular Twitter stats on any topic. Search for your term to generate a line graph that’s scalable over the day, week, and month. You can also see data spread over 90 and 180 days, but you’ll need to sign in with your Twitter account.

No matter the time scale you’re viewing, the stats are broken up hour-by-hour, showing the macro and micro trend at once. Drag your mouse over a section of the time line to zoom in and see exaclty which hour of the the day your term spiked or fell.

Searching for the phrase “World Cup” shows a healthy rumbling throughout May and June (around .10% of all tweets), and a huge spike on June 11th when the games kicked off, peaking at 2.41%.

While a term like this is somewhat predictable, it illustrates the power of a tool like Trendistic for measuring the hourly volume of any topic in the Twitterverse.

2. Twopular

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The Twopular home page offers up 15 to 20 of the most tweeted topics within the last two hours, eight hours, week, month, and ever since the site began aggregating data in December of 2008. If you’re looking to see what’s on top within a given time frame, throw a bookmark here.

But that’s not all that Twopular offers. What makes the site extremely useful for trend trackers is the unassuming “compare” link at the top of the page. Hop in there to see a dynamic line graph that compares up to 10 trends. It will start you off with the most popular topics, but you can add any 10 comma-separated items.

Compare the chatter about seven leading tech companies, or three competing television shows over any length of time, and zoom in on the data down to the minute, if needed. The versatility and simplicity of this comparison tool makes it a great way to quickly reference Twitter trend data.

3. Tweetvolume

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Line graphs not your thing? Do you prefer to visualize your data in plush, colorful bars?

Look no further than Tweetvolume, a super-simple tool for trend comparison over the day, week, and year.

It’s not nearly as granular as the tools mentioned above, but it’s a quick and dirty way to glean “all time” stats.

Say you want compare the popularity of three topics: Justin Bieber, World Cup, and Chicken. Pop them into the topic fields and hit “OK GO!” to generate a graph. Click the time frame buttons on the left to adjust.

As you might suspect, “World Cup” has been neck and neck with “Justin Bieber” over the last day and week, but a year-long analysis shows the boy wonder is far more popular with tweeters than the world’s biggest tournament. “Chicken,” while hardly competitive on a short term basis comes out way ahead when you look at the total tweets aggregated since the site launched in 2007. As we well know, tweeters enjoy talking about their food du jour.

4. PicFog

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As the old saying goes, “A picture is worth a thousand tweets.” If you’re looking for the visuals connected to top Twitter trends (or any trend, for that matter), check out PicFog. It aggregates the photos shared on Twitter via popular sites like TwitPic, yfrog, TweetPhoto, and Twitgoo. The home page will send a flood of photos related to trending topics, but you can search for any phrase or hashtag to kick off a stream of relevant images.

The tool is a comprehensive way to tap the visual sharing power of Twitter around trends relevent to your interest or industry. The site is also popular with journalists looking for real-time images of breaking news events.

5. bitly.tv

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Want to know which videos are being passed around the Twitterverse right now? Popular URL shortener and social data hub bit.ly launched their video aggregation site about six months ago.

There’s no trend comparison data or search available here. Bitly.tv simply tells you what videos are being shared and the volume of sharing (through bit.ly) on Twitter. It provides a fluid interface for browsing and viewing them right on-site. You can page through the videos in real-time, or adjust the slider to see what’s been popular today, what people were tweeting about yesterday, and go back through up to seven days of video trends.

The results you see on Bitly.tv are not chosen or ranked by overall tweet volume, but rather by a proprietary algorithm that bit.ly calls “Bitrank.” It measures “retweets and other social gestures, as well as the number of times other bit.ly users have shortened and shared the same video,” according to the site’s description.

While bitly.tv may not be useful for gathering stats on Twitter trends, it’s a great discovery engine for video enthusiasts, and a window into the trends of Twitter’s visual psyche.