Spare5 is described as 'Got spare time? Get paid when you spend some of it with us.Great companies want your help improving their products'. There are more than 10 alternatives to Spare5 for a variety of platforms, including the Web, Windows, iPhone, iPad and Firefox. The best alternative is Amazon Mechanical Turk. It's not free, so if you're looking for a free alternative, you could try ParticipAid or dscout. Other great apps like Spare5 are SerpClix (Paid), Scale (Paid), Playment (Paid) and Appen (Paid).