For Java and associated ecosystem, Devoxx UK (http://www.devoxx.co.uk) is a pretty good annual conference. You can see talks from last year at https://www.parleys.com/channel/devoxx-uk-2015

I really enjoyed going to the PyCon UK! Everybody was so lovely and really interesting talks. Was of course more python centric

Social Media Summit on in Dublin, Ireland in March. Some good speakers present. http://socialmediasummit.ie/index.php/speakers/

Render-Conf is looking to be good: http://2016.render-conf.com/ It replaces jQueryUK which was great last year.