InstagramSaver is an easy-to-use open source tool which downloads the photos and videos from any Instagram account.
Launch InstagramSaver and you're presented with a clear and simple interface. At a minimum, all you have to do is enter an Instagram user name, click Download, and watch as the program grabs all the photos from that account.
The images are normally saved into a Documents\InstagramSaver\[InstagramAccount] folder, although you can customise this to point wherever you like. Wherever the files are saved, an Explorer folder opens at that location once the download is complete.
By default InstagramSaver won't access videos. If you'd like those as well, click Settings and check "Download videos too".
The program normally downloads files in parallel, with 8 connections open simultaneously. Increasing this figure in the Settings dialog may improve performance, while cutting it should prevent InstagramSaver from hogging all your bandwidth.