If you are on DP you may also use your signature links for demonstrating your writing samples as well.
I am working on this very same thing myself. I have hundreds of samples and I am tired of having to look for them all when a project I am interested in is posted. It takes up too much time. I am currently sifting through all of my samples and classifying them by topic (finance, technology, medical, etc.). Once I am done with that, I am going to convert all of them to PDF format, as I have found PDF is easier to deal with when people have different browsers and operating systems. I am also going to upload them to my site. When I answer ads from now on, I will follow the directions if they are specific (i.e. if they request attached samples, I will attach the PDFs). If there are no specific directions for how to submit samples, I will simply include links to my work so that people hiring writers can visit them and evaluate my writing.