Envelopes are the exception. My 'trick' with envelopes is to send the document unfolded and use a 'manufactured' return address label with logo. But the main issue is that so little is sent by snail mail these days that having printed stationery is simply a holdover from the last century. A PDF by email works great for 95% of correspondence. If you adopt this approach, ideally everyone uses the same template found on your server or Dropbox so that the letterhead design stays 'pure'.
We have standardized on a few other documents as templates: an agenda (which is converted to minutes after the meeting), a memo, a field report, and a notepad for capturing handwritten notes or sketches. The image above gives you an idea of how these templates look. The button will download a zip file of the four templates as Word docs that you can modify.
The agenda and memo are very similar. The key benefit is not having to reinvent the wheel. The embedded table acts as a reminder for including all the background.
The same can be said for the field report. However, we are working towards not having field reports like this at all. The goal is to have a web page on our website (good) or in Basecamp (better) where audio files and photos of the site visit are placed for everyone's reference including a small text paragraph identifying the key issues growing out of the visit.
The notepad template is a throwback to when we used to have our blueprint house make pads of these to use for documenting everything. Nowadays much less makes its way onto a notepad for filing, but it still comes in handy surprisingly often. My favorite technique is to photograph the notepad page with Genius Scan, an Apple App, which will convert it to a PDF and upload it to Evernote, Dropbox or email it. So your note starts as paper and pencil and ends up digital!