Vanessa Gebbie, a writer of excellent short stories and flash fictions, and the person who introduced me to flash fiction in the first place, is running some courses which would be well worth attending.
The first will be at the Anam Cara Retreat in Co. Cork, Ireland, for one week from the 28th May. Entitled 'Short Fiction: So Much More Than It Seems…' it promises to be a wonderful week. More information can be found at http://www.anamcararetreat.com/index.php/workshops/68-short-fiction-so-much-more-than-it-seems.
If you can't make that, then she is also running workshops, masterclasses and one-to-one sessions at this year's Winchester Writing Conference. More details at http://www.writersconference.co.uk/.