TwitterLoader is a free service that allows you to easily search by keyword and then mass follow users returned in the results. No longer do you need to add each Twitter user one at a time.

Simply enter your Twitter username and password to log into your account, once logged in you will see a keyword search box. Enter your keywords separated by commas. Select the users you wish to follow or select all, then mass follow them! You can follow up to 100 users at a time. Hover over users to see their latest tweets.

Normal Twitter limitations apply.

Your privacy is important to us.
Your username and password is not stored on our server.
We will never share your Twitter details with any third party,
except to connect to the Twitter API.