XMPP Account Exporter lets you export your user profile settings, contact list, bookmarks. Not message archive though.

Client apps

Conversations is a great Android client app. Recommended.

Dino is a Linux desktop client. Reliable and slick. Lacks advanced management features e.g. for managing chatrooms - check out Gagim for that. Recommended.

Gajim is a feature-rich desktop client. Has a lot of advanced features but may be clunky or unstable. Recommended.

Converse.js is a web client app. Purely client-side - the JS code runs in your browser, no third party relay server is used.

poezio, profanity, mcabber - terminal-based client apps.