@Background Pony #2481 Ponybooru.org:
Relatively similar to Derpibooru in regards of rules and policies, including DNP policies for artists, and the most active booru of the alternatives available. Some artists who were mad at Derpi moved to this booru and post exclusively on it, and politic pics don't seem to cause controversy there. Recommended if you use Derpi for the active community. Twibooru.org:
The complete opposite of Derpibooru and Ponybooru. It's an archive first and foremost and even has thousands of images that no longer are available on Derpi. It allows all kind of content (including some stuff banned on Derpi) if it's sufficiently pony-related, it doesn't have DNP policies (which means stuff from artists with DNP can and may be uploaded there), disables comments by default and its forum only exists for technical stuff. Recommended if you come to Derpi for the pics rather than for discussion. Ponerpics.org:
The owners not only imported almost all of Derpibooru's content, but they managed to keep the original file IDs and scores, which helps to curate content. Similar to Twibooru, Ponerpics doesn't have a DNP policy, but unlike the former comments and the forum are open for everyone here. Recommended if you want a middle point between the two boorus listed above. Manebooru.art:
This booru has stricter content policies than Derpibooru since it bans all Nazi content and foalcon. Politic discussion is discouraged there as well, since "controversial" art is required to have its comments disabled. Downvotes are disabled as well. Like Ponerpics, Manebooru is importing art while keeping the original IDs, and they have a program where verified artists can have their art imported earlier. Recommended if you don't want to see "controversial" politics at all. Bronyhub.com:
This booru still is in development, but according to its owner it will cover things other boorus ignore. Aside from the WiP booru, a fully fledged forum powered by MyBB, a pastebin service powered by Privatebin, a Discord server and a Rocket.chat server are in the works. If they play their card rights this site could become an interesting hub for the MLP fandom.
Note that my opinions on these sites come from superficial personal experiences (aka using them for a quick fap). More assiduous users and staff from these sites are free to correct me.