Design is communication, and "selling" design, internally and externally, is the difference between executing great work that users connect with, and just being a good pixel-pusher. I think jacquesm has the right idea but muddles it a bit: all great design is sold, not delivered like a pizza. And great design is very much worth selling, for the effect it can have on the world. While selling can seem distasteful (it certainly doesn't come naturally to me), it's a critical skill for designers, entrepreneurs, and founders. Selling is design.
"But is this really MY problem?" In presenting design ie. communicating its value, the roles/responsibilities are not unlike that of a teacher and students: successful delivery of information is the responsibility of the sender. To say eg. "I taught it to them but they didn't learn it" is a contradiction in terms tantamount to "i sold it to him but he didn't buy it." You as the designer are responsible for 1. understanding the problem landscape well enough to deliver a working solution 2. building a decent relationship with the client (internal or external) that you have a good communication channel.
What are the best ways to sell design to non-designers? Clear objectives you've agreed upon and stuck to. Compelling storytelling. Competitive benchmarks. Pure visual WOW factor. $10 usability tests. Man-on-the-street impressions. Rote logic. Brute force. These are the techniques that I've used successfully. They can of course be combined, and there must be many others. ymmv
If "selling" design is problematic and you're not able to push work through to some kind of test environment where real customers can connect with it to PROVE the design works (via sales / leads / engagement, whatever the objective may be), then you might consider joining forces with a fellow writer or designer, or agency, to watch how designers and creative directors successfully bring clients on-board to sell innovative designs.
CAVEAT: There are always critics and naysayers of any sufficiently innovative solution or design. To those people, I say http://purplejesus.files.wordpress.com/2009/03/haters.gif Let them do better, and prove it.