There is many web based Gallery solutions out there and if your looking for something simple, then Plogger could be the PHP Web-based based solution for you. The requirements are basically web hosting of course that has PHP enabled and a MySql back end database, most hosting packages have these as default.
Plogger provide easy picture import by means of uploading to a certain directory on your hosting and pressing import. It allows you to allow downloading of images in zip format though be warned that people might abuse this by trying to grab way too many at once which will not go down well with shared hosting (max cpu time) as it takes time for the host (your web server) to compress the files to a zip.
