A very common criticism of Twitter (other than its uptime) is that it’s just a distraction, “noise” that doesn’t actually help you in any way. Well, here are 12 ways you can use Twitter productively.
MultiMap

The MultiMap twitter bot helps you to access maps, directions and local information by simply sending direct messages via Twitter. You can send a message to fetch local information such as the closest ATM, tourist attraction, park, cinema, theatre or even find entries on wikipedia about what is nearby. Add @multimap as a friend and start sending it commands.
Fuelfrog

Fuelfrog is a service that allows you to track your gas mileage by letting them know the miles you traveled on your last tank, the price you paid, and how many gallons you added to your car. FuelFrog will compile and trend information about your gas mileage, the amount you spend, and more.
Usage: after you sign up for the Fuelfrog service, add @fuelfrog as a Twitter friend. Then send it a message in the format:
miles price gallons
Example: d fuelfrog 342 3.239 10.293
Commuter Feed

Commuter Feed is a free service that lets you post reports on traffic and transit delays in your local area using Twitter. You can also subscribe to your local reports via RSS, so you’ll know what the traffic conditions are like and which routes to avoid.
Add @commuter to your Twitter list. Find your city code (which is your airport code) on the regions page. Then send updates to @commuter in the following format:
@commuter LAX Accident on Sunset Blvd at Vine
which is:
@commuter(SPACE)city-code(SPACE)incident
Then follow your region at its page – here’s Vancouvers feed – which is rarely updated. RSS feeds are available for each region.
Group Tweet

Group Tweet allows you to send private messages to a specific group of users. Excellent for work teams, family members, community members etc.
timer

Timer is a twitter bot that lets you set alarms for things you need to remember. Just add@timer as a friend and send it a direct message in the format:
d timer (number of minutes) (your message)
Example:
d timer 30 pizza is now free
note: 5 minutes is the minimum amount of time that you can set.
itsniceoutside

Add @itsniceoutside as a friend and send it a message with your FULL city info or postal/zip code and get todays weather.
trackthis

Add @trackthis as a friend and get notified via direct message any time your package location changes. Works with FedEx, UPS, USPS and DHL.
More info can be found here: http://trackthis.pb30.com/
junglebot

Add @junglebot as a friend and you can search for books, DVDs and music on Amazon.com.
Usage: d junglebot
For example: d junglebot music warren haynes
More information can be found at: http://www.cartosoft.com/lab/junglebot
Source: Simple Help