Hunting around the net I've found a few new tools that you might want to try out if you're well into Twitter.
Life on Twitter will take a look at about 1,000 tweets and will tell you things like who your best friend is, which days you tweet on most, most used hashtags, influencers, most popular tweets. I'm a bit doubtful about some of the information it came back with but it only took a couple of seconds, so it was of mild interest.
Tall Tweets allows you to write tweets that are longer than 140 characters. You can write out your message and the service will chop it into appropriate sizes and then post them in order. I'd be irritated by this to be honest, and I really would think twice about following someone who did it on a regular basis. However, your call!
Spruce. Very simple - choose an image, choose some words, put the two together and tweet it.
Twitter Archiver lets you easily save tweets for any keyword/hashtag in a Google Spreadsheet. Enter a search query/hashtag and all matching tweets are saved on the Google sheet. You can run Boolean searches as well as advanced Twitter searches.
Twitter RSS Feeds. The link goes to a page that gives an excellent step by step guide on how to create an RSS feed.
Crowdfire is a great tool. It will tell you who you follow who doesn't follow you back, recent unfollowers/followers, people you're following who are inactive, all following (oldest first) and so on. It works automatically and takes only a few seconds.
Tweriod tells you when most of your followers are awake and active, thus informing you of the best time to tweet. For example, for me most people are active at about 3pm on weekdays, then at 6pm, and a few less at about 1pm at the weekend, while during the week, 11 am, peaking at 2pm, and then another smaller peak at 4pm.
Twipho (Twitter photos) is a search engine that just pulls back images that relate to a specific hashtag. I really like this tool - it's simple and easy to use.
(With thanks to Digital Inspiration for the list; go and visit the page since there are many more than I chose to include.)