Do you have copyright or other license information clearly displayed on your website?  If not then it's my understanding that they've not done anything illegal by copying your text.  This may vary depending on which countries the sites are in.

If you do have copyright or other notices, and the copied content is having a financial impact on you then the best thing is to consult a lawyer.  One practical step you can take is report the copying site to Google to get them delisted from search results.