I always, always have a sheet of stamps in my wallet, just in case I pick up a card and need to send it straight away. I am smitten with these whimsical stamps.
Hands down, my favorite stationery line is waste not paper. The printers of this snazzy line pair bright, bold colors with vintage-esque and trendy prints, splashed onto heavy cardstock paper. I have about 10 sets in my desk, and save at least one card from each set--they're just too beautiful! Unfortunately, their website doesn't do the brand much justice, and they don't have a great sales base online... I've found sets of their stationery all over my hometown, and I know they're carried in major stores around the country.
[via google images. (waste not paper)]
check out these sites for some more awesome options in print goods:
ashley brooke designs
Also, search for stationery on etsy for tons of adorable, hand-printed options!