I've removed the fests that didn't run in 2015, but when I do this list for 2016 I'll include as many as I know of and update accordingly as timelines are posted.
January:
hd_erised's 2014 Master Listhd_owlpost's 2014 Master Listmini_fest's 2014 Master Listhrholidays's 2014 Master Listslythindor100's 2014 25 Days of H/D Master Listsmutty_claus's 2014 Master Listrs_small_gifts's 2014 Remus/Sirius Small Gifts Master Listlupin_snape's 2014 Snupin Santa Master Listhoggywartyxmas's 2014 Master Listseverus_snape Master List femslash_remix Master List harrybang Harry Potter Big Bang Master ListFebruary:
hprare_cliche's Valentine's Fest Master Listhp_kinkfest's Master Listhp_3somes's Master List 
torino10154's 2015 5th Annual Porn Sunday Master List!do_me_veela's 2015 Master List hp_het_taboo's Be My Anti-Valentine Wrap Up posthd_familyfest 2015 Master Listhd_remix Vol. 7.0 Master ListMarch:
ron_draco_fest 2015 Master Listhp_goldenage Salt and Pepper fest Master List hp_getlucky 2015 HP Get Lucky Master List hd_hurtfest 2015 Master List femmefest's 2015 Master List April:
hp_deflower 2015 Spring Fest Master List hd_remix's 'That Picture' Flash Fest Master Listdracotops_harry 2015 Master List snape_potter's Snarry-a-Thon 2015 Master Listhp_darkarts's 2015 Horror Fest Master ListMay:
hds_beltane Final Year Master List hp_mhealthfest 2015 Master List harrydracompreg's 2015 Master List dramionelove's Adopt-A-Prompt Fest Master List June:
hd_smoochfest 2015 Master Listdracomalfoy's 2015 Draco's Kinks and Tropes Party Master Listhprarefest's 2015 Master ListJuly:
hp_podfic_fest 2015 Master Listslythindor100's Round 7 of the H/D Last Drabble Writer Standing Taghd_collab 2015 Master Listharrylu 2015 Harry/Lucius Master Listsshg_promptfest 2015 Severus Snape/Hermione Granger Master Listhd_cliche No Masterlist provited yet, but here's the 2015 Fest TagAugust:
snape_potter Snarry Summer Challenge Master Listsirius_black 2015 Dog Days of Summer Master Listseverus_snape 2015 Summer of Severus Comment Fest Master Listhp_crossgenfest 2015 Master Listfortheloveofhp's For the Love of Neville Longbottom Master Listsnarryglompfest Snarry Glomp Fest Master ListSeptember:
dramione_remix's Dramione Remix Round 6 Master Listhp_drizzle 2015 Master Listhd_eighthyear 2015 Master Listbottom_draco 2015 Master Listhp_silencio 2015 Master Listsnaco_soiree 2015 Master ListOctober:
hd_fan_fair 2015 Pottermore Fair Master Listrs_games 2015 Master Listminerva_fest 2015 Master Listhp_creatures's 2015 Halloween Fest Master Listhp_adoptaprompt 2015 Master Listhd_fluff's H/D Fluffy Halloween Fest Taghp_darkages Lucius/Harry Halloween Fest Master Listbirdsofshore's 2015 Rectober List of Reccersdramione_duet's 2015 Master Listhp_humpdrabbles's 2015 Sixth Annual Humpathon Master Listhp_halloween Annual HP Halloween Double Drabble exchange. No master list but here's a link to the 2015 Tag November:
torino10154's 2015 Blowjob Friday Master Listhp_nextgen_fest's 2015 Master Listhd_fanart's 2015 Fest Master Listserpentinelion's Glomp Fest -no fest this yearhp_sexstars no fest this year.hermione_smut 2015 Master Listinterhouse_fest's 2015 Master Listbill_ficathon 2015 Master Listhp_darkarts Darkest Fest Master Listhp_humpdrabbles's 2015 Humpathon Master ListDecember:
hd_erised's 2015 Masterlisthd_owlpost's 2015 Masterlistmini_fest 2015 Masterlistcharlieficathon's Charlie's Birthday Month Masterlistslythindor100's 25 Days of Harry and Draco Final Recapdhr_advent 2015 Masterlistdracoharry100's 2015 Christmas Challenge Tagsmutty_claus 2015 Masterlistrs_small_gifts 2015 Masterlistsshg_giftfest 2015 Masterlisthoggywartyxmas 2015 Masterlistsnape_potter' 2015 Secret Snarry swap MasterlistFor 2015 H/D Fests only check
vaysh's Harry/Draco Fests in 2015. And here's a link to the Harry/Draco Fests in 2016. And of course, for all current fests
potterfests is the place to go. I hope you guys find this useful! And please let me know if I missed a fest. Sometimes it's difficult to keep up with everything. ^^
The 2016 list should be up in the next couple of days. :)
