If you are using twitter to keep your friends in the know on what you are up to and keeping track of them then you might like to know what else you can do with twitter.
Since twitter is a stream of short text messages and it allows you to send directly to another account then it is fairly easy for software to monitor a twitter account and take an action according to the message and optionally send you some information as a reply.
Connecting web applications from Twitter
Since I'm a Google fan the first way I started using this was to update my Google Calendar. Twittercal allows me to send a direct message and have an appointment added to my calendar. It uses the same syntax as the "Quick Add" feature. "d gcal appointment with doctor at 6pm Thursday" would add the required appointment. The "d gcal" means "send a message directly t the account 'gcal' and not to my twitter feed."
I use a nice little to-do system called Remember The Milk. This to-do system ties well into Google Mail and Google Calendar as well as twitter. Not only can you add to-do items you can retrieve them based on the date due, which of your lists it is in or even according to tag, all from twitter.
If you're after an even more advanced reminder system then the one that I'm currently testing, IwantSandy, seems to be a winner. You can add reminders, appointments, to-dos and things you just want to remember right from twitter and then even ask a question. You can tag items and even specify how you want to be reminded, twitter, email or mobile. This may be the killer reminder system given that it ties in to your email system and twitter so well.
If, on the other hand, you want something simple then Twitternotes just stores notes in a simple database with optional tagging.
If you send and receive a lot of freight then you might like track this. Once you follow it you send it a direct message "d 123456978321 New camera" and every time it changes location you get a tweet.
If you have to track a large number of leads and want something to pick one at random and remind you then Salestwit can do that. Feed in your contact list and it feeds you one at random every day, week or a configurable delay.
If you are organising an event or a group going to an event then @eventrack uses a tagging system to collect information from a large number of places, including twitter. This is a great tool for collecting video, pictures, web posts and tweets about an event all in one spot.
These are my favourite online applications that connect to twitter. You can find more at the Twitter Fan Wiki.
Finding more followers
The best way to get more people to follow you on Twitter is to follow them. If you are putting useful information in your twitter feed and blog then find others who are interested in the same areas as you and follow them.
To find people talking about my areas of interest I use TwitterTroll - an excellent search engine. The advantage of this is that I also get great information from others as well as people I'd like to connect with.
If you're going to be following a lot of people and making a lot of twitter updates yourself you're going to need a good Twitter client. On my Mac I use both Twitterific and a Dashboard widget, I suggest you spend some time going through the various options till you find one that suits you. Check them out at the Twitter downloads page and on the fan wiki.