I've seen about as much "going green" marketing as I think I can take...however there are a few things that we've recently been doing for some customers which actually falls into the whole less paper, less waste basket.  So I thought I'd share accordingly.

If your company uses any type of printed materials for either contracts, sales orders, forms, etc. you should consider perhaps going with a more dynamic solution of taking your contracts and forms to PDF's which can be signed digitally pretty easily now, and emailed back without a single sheet of green gold being wasted. 

Companies like eFax (www.efax.com) have really stepped it up and have even added a free service to their monthly subscribers by allowing them to upload and store and then use their scanned in digital signature for even more paperless processing.

ColdFusion FlashDocs/PDF
If your website or web application is ColdFusion based, you're just about as close as you can get to already having this functionality added to your system.  Simply by using ColdFusion 7&8's <cfdocument> tag like the following will instantly transform your page into a PDF which can be enhanced with dynamic data from your application/forms very quickly:

<cfdocument format="pdf" name="mydocument">
<cfloop index="x" from="1" to="40">
<p>
doloras lorem upsom doloras paris hilton is my hero loreum ipsom dsoio foom an to dht end of the world
will anyone actually read this probably not but let me put more realtext in so it flows a bit nicely
<cfloop index="y" from="1" to="#randRange(1,9)#">This sentence will appear a random amount of time.</cfloop>
</p>
</cfloop>
</cfdocument>

.NET and Tall Components
If you're a .NET firm or company, there's quite a number of solutions out there for you as well.  We've personally just worked on a project for Westcor Land Title www.ewestcor.com where all of their jackets and other assorted loan closing documents are generated on the fly.  Thereby reducing their need to request hundreds of these jackets and documents from a printer, thus reducing paper.

For that project we worked with TallComponents www.tallcomponents.com/ to accomplish this task which really allows for quite a bit of customization even more so in some respects than Adobe's solution.

For you PHP and Ruby folks, I did find a few quick and free solutions to generate PDF's from PHP.  The one that seems to be the easiest to use, but doesn't do a whole lot of fancy effects is www.fpdf.org
So you're in good shape as well.

Go Green By Going Red
So you can go a bit greener by using the "Red" logo Adobe PDF format in a host of different ways on almost every type of web programming language in use today.  So save a tree...plant a PDF on your web app today.