When I go through the process of building a competition slide for a pitch deck I like to include several "forms" or competition.

1. Monopolistic Competition: Big players in your space, these are the Microsofts, Oracles, Google's of the world.

Tools to use: Public companies announce quarterly earnings. Understand where their revenue is coming from and what's growing the fastest. ex. http://www.sec.gov/Archives/edgar/data/1288776/000128877614000075/goog10-qq32014.htm#sE456F21B4F58076BCE0E8E07A40E64F4
It's also worth reading into what financial analysts say about each quarterly earning report. They are normally small picture thinkers but they almost always focus in on what the company is spending most of it's growth efforts on.

2. Distribution Competition: These are companies that will be fighting for the same distribution channels and advertising channels as you.

Tools to use: If yours is a mobile app, the best tools is App Annie, look at apps that compete in your category. You will have to fight these apps on download volumes and ratings even if they don't directly compete.
http://www.appannie.com/apps/ios/top/united-states/social-networking/?device=iphone

3. Audience Match Competition: These are companies that target a similar demographic profile to yours. Similar to distribution matching, these competing companies will be fighting for the same ad dollars.

Tools to use: Some of these are dated but it is a good list: https://blog.kissmetrics.com/25-sneaky-online-tools/

4. Use Case competition: These companies have a similar use case or have a solution to your problem (even if the solution is different)

This could be as simple as you're a note taking app and a use case match cold be a notebook, they are still worth brining into the slide as they inflate your solution as the obvious better solution.