I don't use a lot of tools for my startup, just this ones:
-intercom.io - really great to schedule automated messages and it can be synced with your database and have custom fields. Very easy to setup
-Google Apps (analytics,gmail, webmaster tools)
-Monitor Backlinks (my own startup) to build links to my website
Disclaimer: I am the CEO & Founder of Monitor Backlinks
My specialty is developing Digital Creative Strategies for Marketing Campaigns.
A great starting point is Google's Think Insights Toolbox: http://www.google.com/think/products-tools/
Using the data from those tools you can glean insight out of a brand which you can then use to come up with ideas that can be refined into concepts. A concept is when an idea takes on the shape of an execution, like a website or app.
Let me know if that was helpful.
My favorite FREE tools...
-Hunter.io. The easiest way to get a person's email with just a click! It's always with me in Chrome.
-Plutio. Manage your tasks, invoices, etc.
-Grammarly + Hemingwayapp. Correct your grammar and style.
-Buffer. Schedule your content so you can keep your consistency up
-Findthatlead. Find leads, emails, and data on your prospects.
-Neverbounce. Clean list of emails to reduce the bounce rate
-Sumo. Free tools for your websites (heat-map, overlays, etc.)
-Newsfeed eradicator. Eradicate the newsfeed from Facebook so you can remain focused
inbox when ready. Need to check a specific email in your inbox but don’t want to get distracted but new requests? Amazing productivity tool
-Thrive Headline Optimizer. A/B test your headline and get the statistics.
-Buzzbundle. Check the buzz on Social Media about specific keywords so you can respond actively to your target market