You don't have to spend thousands on media lists anymore. You can easily track down journalists, editors, bloggers, etc. on Twitter. Remember to build a relationship with the media and don't use Twitter as an excuse to spam them or beg them to write a story about you or your company. Make a comment about their article/story and create a rapport with them over time (the same rules to offline media relations still basically apply). Be professional and read past articles to understand their writing style and focus. Also, look at who follows the media and follow influential industry leaders - another good way to target your Twitter followers.
Here my top 3 recommended Twitter media resources:
1. MediaOnTwitter - This is a handy media database resource that breaks down journalists/writers by first name, Twitter ID and URL, media outlet, title and country. MediaOnTwitter makes it easy to follow media and stories that fit with your industry/company.
2. Muck Rack - Subscribe to their daily email digest to get the latest list of journalists who contribute on Twitter. Muck Rack breaks down their 'beats' ranging from arts and entertainment to politics. This is a great way to search for late-breaking news in your industry and to connect with journalists who might be interested in your newsworthy story. However, as I mentioned above, don't spam the media. Reply to their tweets and stories in a real, genuine way.
3. JournalistTweets - Check out what journalists are saying on JournalistTweets. This Twitter media resource connects journalists with PR professionals. However, it's a handy way to research journalists by country and follow the latest scoop with industry news. You can set up email alerts and track what journalists say about you and your company on Twitter.