It depends on whether it is for Retail or Hospitality really. There are not many decent cheap/free ones out there, they are cheap or free for a reason.
UK EPOS is one of the cheap ones if you want basic functionality but if you have issues they are not the best at helping you out. Wasp is another cheap one.
Depending on what you want and how you plan to use it, one option would be to get the free demo version of Microsoft Dynamics (RMS or POS2009). With that you can use a good amount of the package without restriction (the back office functionality and stock control etc.) The restriction comes with the front end till program, you can only put a maximum of 5 lines on one transaction, but if you are not planning on selling more than 5 things in one go then that would be a way of doing it for free. I used to run an E-Commerce web business selling EPOS Hardware on the free demo version of RMS/POS2009 so I know it works.
I think you can get it here, and there are some other suggestions to try there.http://softwaretopic.informer.com/microsoft-dynamics-pos-2009-trial/
One word of warning though, Microsoft no longer offer support on the product, they bought AX and are putting all of their efforts into support Microsoft Dynamics AX instead, so it might not be a long term solution.
I used to work for a Retail EPOS provider that dealt with tinpot small companies, but now work for NCR in the hospitality world. I think the NCR product might be a bit OTT for anything you would need
we deal with more the BK, KFC and Nando's of this world.
Let me know what you are after and if I can give any advice I will. I can even provide you with a Polish Chubbsy forum member who will support POS2009 for pint and a packet of crisps..