Before visiting WisCon last year, I printed a set of 400 bookmarks to distribute promoting my work (including my ebook Aqua Vitae). The bookmarks were designed by a friend, the multitalented Matthew Luckow, and printed using VistaPrint.
Although I don't recall ever seeing a straightforward bookmark option, there are several ways to print bookmarks through VistaPrint, including using the business card option to make slightly smaller-than-usual ones. I've seen many lovely examples, and can say from long experience that they work perfectly well to mark your place in a book. However, I decided to follow the advice of this article and created my bookmarks as postcards.
Basically, when uploaded, the images were oriented thus (front side on the left of the screen, back side on the right).
I ordered 200 of them, which, sliced in half with the use of a library guillotine (that is, a large bladed paper cutter I have access to through my college library. If guillotine is not the proper word for that implement, I do not care to use the proper word) produced 400 bookmarks that I still have not been able to entirely use up, despite passing them out at multiple conventions and including them with paperback review copies. As I'm very satisfied with the finished design, I don't mind having so many, but if I had expected to need updated information more frequently--for example, to link to this new blogspot site--I would have chosen a smaller print run (with a caveat I'll get to soon).
Additional advice from my experience:
Be sure to get a VistaPrint discount code. This can be done by subscribing to their mailing list, joining other groups that distribute coupons, or by borrowing a code from a friend who has one. But until you have a discount to use, beware, VistaPrint prices add up very quickly. They charge, from what I can tell, for each subset of a service. Printing my gorgeous bookmarks in color on both sides added at least a dozen dollars to my order. Also, because elaborating on each aspect of the card becomes an added charge, I'd suggest looking for coupons that deduct from the price of your complete order rather than giving individual services for free or at a reduced price--you'd still have to pay for the other services.
While the RedRoom article suggests the finished cards will be about a penny each, mine were closer to four cents. Not a bank-breaker, although if you pay tax (self-employment included) for your writing income I suggest you keep the receipt to deduct from your 1099-MISC royalty profits.
Be careful to orient the images on the postcard the way the article shows you! Matthew and I followed the instructions carefully (re-uploading the files to make sure) and our bookmarks turned out fine. Otherwise, they'd have been printed with one side upside down relative to the other. Still usable as bookmarks, but awkward. This would be a difficulty, considering there are hundreds of them.
Also, take care in how you cut the postcards. You get two to four bookmarks per card, depending on the orientation, and that becomes a lot of cutting. It's tempting to chop through several at one time to lessen how long you'll take at the guillotine--my 200 postcards took nearly a half hour. However, the best results come from cutting one card at a time, as the glossy paper stock doesn't slice easily in a thick stack. I lost several bookmarks in trying. They do slice better with the glossiest side facing down, at least with the old blade I was using. Sharper ones may manage more, but be conservative until you're sure.
For that matter, when designing the image to upload on VistaPrint, add very generous margins. You'll need them when cutting the finished product. VistaPrint's printing sometimes leaves blank slivers on the edges of cards. You can decide whether they're worth trimming off if they occur. I left them for the most part because they were minor and I didn't want to risk slicing a card lopsided.
The price per card drops drastically as you make larger and larger orders. However, if you may be updating your author information anytime soon, you won't want many more cards than you can distribute. The best thing is probably to be consistent so you don't need the updates--I figure this blogspot site is here to stay, so the next time I print a batch of bookmarks, I'll order more of them.
And I will order more and continue to use them. I don't think bookmarks are the most effective way to promote a book (reviews & reader chatter/word of mouth are best, along with sound writing that's worth chattering about). I did see small upswings in sales after the convention, although given I was talking to people and attending readings I can't attribute that for certain to the bookmarks. Yet, like business cards, they're a good way to leave someone your information for follow-up. You wouldn't want somebody to ask if you have a card and not have one to offer them. Not to mention they're just plain fun to make and give away!
For more tips on formatting for people who are writers, not designers, see my post about Print-On-Demand (CreateSpace, Lulu, etc) Formatting for Better Royalties. Lots of information from this post--plus much more--can be found in The Starter Guide for Professional Writers, my book introducing new and hopeful writers to the world of revising, marketing, and publishing your work.