Currently erupting:

Ambrym (Vanuatu): active lava lakes in several craters (updated 12 Jul 2016)
Bagana (Bougainville Island, Papua New Guinea): intermittent mild ash emissions (updated 29 Dec 2016)
Barren Island (Indian Ocean): strombolian activity in summit crater, lava flow effusion (updated 20 Feb 2017)
Bogoslof (United States, Aleutian Islands): intermittent strong explosions (updated 8 Mar 2017)
Chirinkotan (Northern Kuriles, Russia): possible large explosion on 28 Nov 2016 (updated 28 Nov 2016)
Colima (Western Mexico): intermittent low-energy ash emissions (updated 12 Feb 2017)
Dukono (Halmahera): mild strombolian activity, continuous intense ash emissions (updated 29 Dec 2016)
Erebus (Antarctica): active lava lake in summit crater (updated 8 Dec 2014)
Erta Ale (Danakil depression, Ethiopia): lava lake overflowing, caldera flooded with new lava flows, collapses inside southern caldera (updated 27 Jan 2017)
Fuego (Guatemala): lava flows on S and W flanks, lava fountaining from summit vent (updated 9 Jan 2017)
Gamalama (Halmahera): small ash eruption on 3 Aug 2016 (updated 5 Aug 2016)
Heard (Australia, Southern Indian Ocean): strombolian activity in summit crater, lava flow effusion (updated 9 Feb 2017)
Ibu (Halmahera, Indonesia): stromolian and phreatomagmatic explosions (updated 29 Oct 2015)
Kilauea (Hawai'i): new surface lava flows from breakouts N and NE of Puu Oo since 24 May 2016 (updated 29 Sep 2016)
Klyuchevskoy (Kamchatka): strombolian activity from summit crater, mild to moderate ash emissions (updated 2 Mar 2017)
Langila (New Britain, Papua New Guinea): likely lava flows or lava dome extrusion, strombolian activity (updated 29 Dec 2016)
Lopevi (Vanuatu): probably strombolian activity in summit crater (updated 13 Jan 2017)
Masaya (Nicaragua): active lava lake ini summit crater (updated 12 Jul 2016)
Nevados de Chillán (Central Chile): intermittent ash emissions (updated 9 Jan 2017)
Nyiragongo (DRCongo): new vent on crater floor (updated 9 Sep 2016)
Ol Doinyo Lengai (Tanzania): effusion of natrocarbonatite lava inside the crater (updated 8 Jul 2013)
Pacaya (Guatemala): strombolian activity in summit crater, lava flow effusion (updated 2 Mar 2017)
Popocatépetl (Central Mexico): degassing, sporadic explosions, slowly growing lava dome (updated 27 Nov 2016)
Reventador (Ecuador): lava flow on SW flank (updated 9 Jan 2017)
Sabancaya (Peru): frequent moderate explosions, intense ash emissions (updated 29 Dec 2016)
Sakurajima (Kyushu, Japan): sporadic vulcanian explosions from Minamidake and Showa crater (updated 22 Aug 2016)
Sangay (Ecuador): mild strombolian activity in summit crater (updated 20 May 2016)
Santiaguito (Guatemala): intermittent strong explosions from growing Caliente dome (updated 25 Aug 2016)
Semeru (East Java, Indonesia): growing lava dome, mild strombolian activity in summit crater (updated 10 Oct 2016)
Shiveluch (Kamchatka): growing lava dome (updated 29 Dec 2016)
Sinabung (Sumatra, Indonesia): continuing pyroclastic flows (updated 9 Jan 2017)
Stromboli (Eolian Islands, Italy): weak, intermittent strombolian explosions (updated 29 Dec 2016)
Suwanose-jima (Ryukyu Islands): intense strombolian activity from Otake crater (updated 28 Nov 2016)
Villarrica (Central Chile): small active lava lake in summit crater (updated 23 Aug 2016)
Yasur (Tanna Island, Vanuatu): ash emissions, weak strombolian explosions (updated 15 Sep 2016)

Eruption warning / minor activity:

Aoba (Vanuatu): steaming, possible ash emissions (updated 14 Aug 2016)
Aso (central Kyushu, Japan): degassing, sporadic steam / ash explosions (updated 8 Oct 2016)
Awu (North Sulawesi & Sangihe Islands): seismic unrest, eruption warning (updated 13 May 2016)
Batu Tara (Sunda Islands, Indonesia): unknown, possibly weak strombolian activity (updated 25 Aug 2016)
Bezymianny (Central Kamchatka Depression): new activity since around 12 Dec (updated 29 Dec 2016)
Bristol Island (United Kingdom, South Sandwich Is): eruption seems to have ended (updated 14 Sep 2016)
Bromo (East Java, Indonesia): intense degassing, intermittent ash emissions, crater glow (updated 10 Oct 2016)
Bulusan (Luzon Island, Philippines): intermittent ash emissions, intense degassing (updated 29 Dec 2016)
Canlaon (Central Philippines): degassing, sporadic ash emissions (updated 29 Jul 2016)
Cerro Negro (Nicaragua): increased earthquake activity (updated 16 Feb 2016)
Chaitén (Southern Chile and Argentina): seismic unrest (updated 22 May 2015)
Chikurachki (Paramushir Island): steaming, degassing (updated 23 Aug 2016)
Chirpoi (Kurile Islands, Russia): degassing, steaming (updated 29 Jul 2016)
Cleveland (Aleutian Islands, Alaska): sporadic explosions (updated 5 Feb 2017)
Copahue (Chile/Argentina): mild ash and steam emissions (updated 29 Dec 2016)
Ebeko (Paramushir Island): intermittent mild ash emissions (updated 1 Mar 2017)
Etna (Sicily, Italy): ash emissions from SE crater (updated 19 Apr 2014)
Fort Selkirk (Canada)
Karangetang (Siau Island, Sangihe Islands, Indonesia): rockfalls, glowing lava dome (updated 13 Jan 2016)
Karkar (Northeast of New Guinea): possible ash eruption on 1 February (updated 27 Mar 2014)
Karymsky (Kamchatka): weak activity (rare explosions?) (updated 16 Jun 2016)
Kerinci (Sumatra): intermittent ash explosions (updated 5 Jun 2016)
Krakatau (Sunda Strait, Indonesia): unrest, eruption pause or eruption ended (updated 22 Feb 2017)
Lascar (Northern Chile): sudden explosion on 30 Oct 2015 (updated 31 Oct 2015)
Llaima (Central Chile and Argentina)
Lokon-Empung (North Sulawesi, Indonesia): seismic unrest, eruption warning (updated 9 Mar 2016)
Manam (Papua New Guinea): occasional ash emissions, thermal anomaly at crater (updated 13 Jul 2016)
Merapi (Central Java, Indonesia): sporadic phreatic explosions (updated 21 Aug 2015)
Michael (United Kingdom, South Sandwich Is): heat signal from summit crater, unknown eruptive activity (updated 28 Nov 2016)
Momotombo (Nicaragua): intermittent vulcanian explosions (updated 29 Mar 2016)
Nevado del Ruiz (Colombia): intermittent mild to moderate ash emissions (updated 18 Oct 2016)
Niigata-Yake-yama (Honshu): sporadic explosions, seismic unrest (updated 8 May 2016)
Nyamuragira (DRCongo): active lava lake in summit caldera (updated 2 Feb 2017)
Piton de la Fournaise (La Réunion): eruption ended 27 Feb 2017 (updated 1 Mar 2017)
Poas (Costa Rica): sporadic phreatic explosions (updated 29 Jul 2016)
Rincón de la Vieja (Costa Rica): sproadic hydrothermal explosions (updated 3 May 2016)
Rinjani (Lombok): sudden eruption on 1 Aug 2016 (updated 29 Sep 2016)
San Miguel (El Salvador): seismic unrest, inflation, strong degassing (updated 19 Jun 2016)
Sangeang Api (Indonesia): weak lava extrusion from summit crater (updated 11 Nov 2015)
Sete Cidades (Azores)
Soufriere Hills (Montserrat, West Indies (UK)): seismic unrest, occasional light ash venting (updated 21 Mar 2013)
Telica (Nicaragua): lava glow from crater, degassing, occasional light ash emissions (updated 9 May 2016)
Tungurahua (Ecuador): inflation, eruption warning (updated 5 Jun 2016)
Turrialba (Costa Rica): sporadic mild ash emissions (updated 29 Dec 2016)
Ubinas (Peru): intermittent ash explosions (updated 4 Oct 2016)
Ulawun (New Britain, Papua New Guinea): degassing, ash venting (updated 5 Aug 2013)
White Island (New Zealand): ash venting from 2012 lava dome (updated 13 Sep 2016)
Zavodovski (South Sandwich Islands (UK)): strong steaming, degassing (updated 18 Jun 2016)
Zhupanovsky (Kamchatka, Russia): steaming / degassing (updated 20 Nov 2016)