As a new stationery company, I can offer some words of advice.
First of all, you might consider becoming a member of the national
Greeting Card Association...they offer some great insight into the
industry, in addition, their site has links to industry vendors such as
envelope, paper and other important prodution manufacturers.
I would also subscribe to (if you have not done so already) Greetings, etc. the industry trade magazine.
As part of your business plan development, you`ll need to do a ton of
research at both stationery stores and on-line...it might be a good
idea to contact one of the small-ish firms out there and ask them some
questions, as it relates to production, pricing, distribution, etc.
The stationery industry is very competitive, but there is always room for new, fresh and creative ideas.
All the best and much success!