NextGen Gallery is a highly popular gallery plug-in for WordPress users. This is a fully responsive gallery design that allows you to choose from many different styles. The free version includes five gallery displays, four built-in lightboxes, social sharing option, Meta-Data tags, watermarking, Zip Imports, Image Backup, use on unlimited sites, and hundreds of other options. The Pro versions enable eCommerce. This plug-in has had more than 12 million downloads.