Many investor and sales presentations include logo pages. Improve the quality of these slides significantly by not picking the first image that pops up in Google image search:
  1. Visit the company's web site to see what the latest logo of the company in question is, logos get updated frequently
  2. Set the Google image search options to large format
  3. Pick a correct, huge logo
  4. Paste it in your presentation, reduce to the correct size, hit compress images
Companies with a good PR department have high-resolution images of their logos on the web site. Use them.