Tweetmeme, the popular aggregator of the most retweeted stories on Twitter, has just released a variety of new features, some of which we previewed earlier this month. These updates are designed primarily for websites that use the Tweetmeme button (like Mashable), which makes it easier for visitors to share stories on Twitter.

As expected, the updates include a new image-based button option for services that don’t support JavaScript (this will also work in RSS feeds or emails), new analytics inside Tweetmeme’s WordPress plug-in, and new retweet chicklets.

Another significant enhancement is the ability to choose your own URL shortener, which will allow you to consolidate data from retweets that come from the Tweetmeme button with your URL shortener of choice. Currently, Tweetmeme is supporting 11 different URL shorteners – seemingly the most popular ones like Bit.ly, TinyURL, and is.gd.

Ultimately, a smart set of changes that extends the reach of retweeting while also giving publishers a bit more control over how their stories are shared.

Retweeting Resources from Mashable

1. HOW TO: Retweet on Twitter

2. The Science of ReTweets

3. Repeets Tracks Twitter’s Hottest Retweets

4. DailyRT Ranks Twitter Retweets

5. DMfail Fails, Reborn as Re-Twit’d

6. The Retweeting Movement Adds Some Powerful New Tools

7. Retweet iPhone App for Twitter

8. Facebook Needs Its Own Version of the Twitter Retweet

Tags: retweeting, tweetmeme, twitter