I ask for donations - and I have been VERY pleasantly surprised at the great response. At first, I felt "weird" asking for free stuff from boutique owners, but I've met some great shop owners and formed some great professional relationships. Basically, boutique owners who are saavy know that any extra advertising is good for their site - so many are willing to donate a product to increase traffic to their sites. That being said, I have a main site, ParentingPink.com that my blog is attached to, so shop owners like the idea of advertising on a site as opposed to a blog - but it never hurts to try.
When I find a really cute boutique that I like (things I would buy my own daughters) I email the owner, plead my case, and ask for a donation for the contest of their choice. My contest participants have been very generous in their donations & I am grateful. I think you will find them the same way too.
Good luck! Please feel free to email me if you want more details or info.