If you are collecting Lufthansa’s Miles & More miles then this is an option for topping up your balance, albeit not by much!
Miles & More is currently offering 100 M&M miles for every hotel review you write for www.holidaycheck.com. Details of the promotion can be found here. You can also earn airberlin topbonus miles or BalticMiles for writing reviews for the site, although these are minority interests for most UK residents.
Back in October, I wrote this post about earning Miles & More miles for writing Tripadvisor reviews submitted on the Indian website. This offer is still running, paying 100 M&M miles per review. Technically, the rules say that the hotels you review should be in India, but so far people have received the miles wherever the hotel is based.
You can now double up, earning 100 Miles & More miles from the same review on both Holiday Check and Tripadvisor! (Technically, of course, you shouldn’t do this so I would change the text around a bit on each review …..)