I'm a huge fan of Pinboard. It's speed, versatility and API are surpassed by few other services like it's kind. In fact, it's Pinboard's API that allows for a barrage of great apps to exist. One such app is Pinswift, on iOS. Phillip leverages Texttool and Drafts to take advantage of Pinswift's URL scheme.
Pinswift’s url scheme to browse a list of tags is straightforward, according to its documentation, you can queue up to three tags plus an username, however, in my tests I had no problem using more tags, although you need a touchdown to catch any result this way.