You have a couple of options. Sabrina gave you great advice: give credit where credit is due and disassociate yourself from any affiliation with those sites. Link back to those sites where appropriate. I would also suggest that whatever you’re saying or doing in your app should not be derogatory toward those trademarked companies in any way. You certainly do not want to draw attention to your use of them.
A trademark doesn’t necessarily mean that no one else can use that name. If it did, there would be a lot of bloggers, journalists, and websites in trouble who make commentary and use those trademarked names in their writing. A trademark means that others can’t use a similar trademark with similar goods or services.
Under nominative fair use, people can use another’s trademarked item to refer to the trademark owner’s actual goods or services that are associated with the mark. This is because the trademark is being used to describe those things and it does not imply ownership or affiliation of any kind.
Another option would be to reach out to those companies in writing and ask for permission. Again, it would be important that your app doesn’t appear to be derogatory in any way. Of course, you may or may not hear back from them.
And, as Sabrina said, if you elect to use those names because you believe it falls under nominative fair use (check with an intellectual property lawyer) and then you hear back from those companies about your use of the names in the app or on your website, take those names out.
If you’d like to chat with an intellectual property lawyer about your desire to use trademarked names in your app, check out. You can consult with an intellectual property attorney and get the answer that you need for a fair flat rate. Hope this helps!