I had "Both Sides of the Sun" feature my cards on their blog:
http://www.bothsidesofthesun.com/?p=326I loved the pictures they took with my product. I think that it was worth while for me. My traffic went up when the blog post went up. I constantly get hits from that post. My advice is to research the blog. Does your product fit in the blog and the other way around? What's their traffic like?
Yes, there are a lot of opportunities to collaborate with bloggers and not spend a dime. I am constantly looking for the right sellers to feature on my blog: www.raquelmanuela.com.
Let me know if you would like to collaborate. :)