Ok, I get asked all the time about stationary and the like, so here's a small list of some places I'm fond of ordering or buying from (keep in mind I'm in Canada):
My number one:
She's a sweetie and will respond to you within like seconds of emailing her a question. And her prices just plain rock.
Very cute stuff, cheap shipping as well.
Great for rolls of stickers and some stationery - also a great place for cheap tuck-ins. Frequent sales.
If you're a geek - then this is the place to get stationary. I've bought Alice in Wonderland, Lenore, Vampire and loads of other stationary (paper and envelope sets) from them. At about $5 a pop, it's not too bad if you're an addict like me. hehe
Good for cards - fairly good prices. Comparative to vistaprint.
Morning Glory (known especially for Blue Bear). This is the stuff you would pick up if you go stationary shopping in Chinatown (anywhere in north america).
I haven't ordered from them before, but I've been told only good things about them. Let me know about your experiences with them if you've ordered from them before.
Should also be mentioned - but I haven't ordered from them, either.
Search around Etsy.com for stationery, you'll usually find some really nice stuff. (I have my own etsy stationery store)
(I'm in Ontario Canada, so a lot of these may be province or country specific)
Buck or Two
Everything For a Dollar Store (EFADS)
stores in chinatown
Sandylion Sticker factory (if you're in Ontario)
Check stores that are going out of business for good deals on random things. You would be surprised at what you can use as a tuck-in.