Currently erupting:

Ambrym (Vanuatu): active lava lakes in several craters (updated 5 Dec 2013)
Bagana (Bougainville Island, Papua New Guinea): ash explosions (updated 10 Dec 2013)
Barren Island (Indian Ocean): new eruption in mid October 2013 (updated 17 Oct 2013)
Batu Tara (Sunda Islands, Indonesia): strombolian explosions, ash plumes up to 500 m, extrusion of a small lava dome with rockfalls (updated 6 Nov 2013)
Cleveland (Aleutian Islands, Alaska): continuous small eruptions (updated 6 May 2013)
Colima (Western Mexico): explosions and lava flows (updated 5 Dec 2013)
Dukono (Halmahera): thermal anomaly, probably small explosive activity in summit crater (updated 30 Nov 2013)
Erebus (Antarctica): active lava lake in summit crater (updated 21 Jan 2012)
Erta Ale (Ethiopia): active lava lake in northern pit crater, active hornito with intermittend flow in southern crater (updated 11 Jan 2013)
Fuego (Guatemala): strombolian activity at summit, lava flow emission on upper slopes (updated 10 Dec 2013)
Ibu (Halmahera, Indonesia): growing lava dome, seismic unrest (updated 23 Oct 2013)
Karymsky (Kamchatka): occasional small explosions, thermal anomaly (updated 6 Nov 2013)
Kilauea (Hawai'i): lava lakes in Halemau'uma'u and Pu'u 'O'o, lava flows on coastal flat and weakly active ocean entries (updated 13 Aug 2013)
Klyuchevskoy (Kamchatka): ash emissions (updated 12 Dec 2013)
Nyiragongo (DRCongo): active lava lake in summit crater (updated 12 Jun 2013)
Ol Doinyo Lengai (Tanzania): effusion of natrocarbonatite lava inside the crater (updated 8 Jul 2013)
Pacaya (Guatemala): strombolian activity and lava flow (updated 10 Dec 2013)
Paluweh (off Flores Island, Indonesia): active growing lava dome (updated 12 Aug 2013)
Reventador (Ecuador): ash explosions, occasional pyroclastic flows (updated 14 Nov 2013)
Sakurajima (Kyushu, Japan): constant ash emissions and strong explosions (updated 10 Dec 2013)
Santa María / Santiaguito (Guatemala): Santiaguito volcano (Guatemala): lava flow on south flank of dome becomes more active (updated 10 Dec 2013)
Semeru (East Java, Indonesia): growing lava dome, ash venting and small to moderate explosions (updated 18 Oct 2013)
Shiveluch (Kamchatka): growing lava dome, incandescent avalanches, occasional explosions (updated 11 Dec 2013)
Sinabung (Sumatra, Indonesia): vulcanian explosions, ash venting (updated 12 Dec 2013)
Stromboli (Eolian Islands, Italy): continuing lava overflows (updated 3 Nov 2013)
Suwanose-jima (Ryukyu Islands): Mt Ontake volcano of Suwanose-jima Island, Japan (updated 6 Dec 2013)
Yasur (Tanna Island, Vanuatu): ash emissions, weak strombolian explosions (updated 20 Nov 2013)
Zhupanovsky (Kamchatka, Russia): new explosive activity since 23 Oct (updated 6 Nov 2013)

Eruption warning / minor activity:

Bezymianny (Central Kamchatka Depression): slow lava flow extrusion from dome (updated 13 Oct 2013)
Chirinkotan (Northern Kuriles): unspecified activity - possibly lava flows (updated 22 Nov 2013)
Copahue (Chile/Argentina): ash venting (updated 16 Nov 2013)
Dieng (Central Java): increased degassing (updated 28 Mar 2013)
Etna (Sicily, Italy): degassing, seismic unrest (updated 13 Dec 2013)
Galeras (Colombia): sporadic ash emissions (updated 5 Dec 2013)
Heard (Australia, Southern Indian Ocean): likely lava lake in summit crater (updated 6 Dec 2013)
Iliwerung (Lesser Sunda Islands): possible submarine eruption from Mt Hobal on 20 August (updated 20 Aug 2013)
Jebel Zubair (Red Sea): no signs of activity after 24 Nov 2013 (updated 26 Nov 2013)
Karangetang (Siau Island, Sangihe Islands, Indonesia): lava extrusion at summit crater, strombolian activity, glowing avalanches (updated 4 Sep 2013)
Ketoi (Kurile Islands, Russia)
Kirishima (Kyushu): degassing, slightly increased seismic activity (updated 30 Jul 2012)
Langila (New Britain, Papua New Guinea): occasional ash explosions (updated 22 Nov 2013)
Lokon-Empung (North Sulawesi, Indonesia): small explosions, lava flow? (updated 24 Sep 2013)
Manam (Papua New Guinea): degassing, occasional ash venting (updated 5 Dec 2013)
Marapi (Western Sumatra, Indonesia): occasional ash explosions (updated 9 Dec 2013)
Merapi (Central Java): sporadic phreatic explosions (updated 12 Dec 2013)
Nevado del Ruiz (Colombia): seismic unrest (updated 7 Oct 2013)
Nishino-shima (Volcano Islands, Japan): degassing, possible end of eruption (updated 12 Dec 2013)
Papandayan (West Java): strong hydrothermal activity, increased seismicity (updated 6 May 2013)
Poas (Costa Rica): occasional small phreatic explosions from lake (updated 22 Aug 2013)
Popocatépetl (Central Mexico): steam/gas/ash emissions (updated 9 Dec 2013)
Rabaul (Tavurvur) (New Britain, Papua New Guinea): weak ash explosions (updated 5 Dec 2013)
Raung (East Java): strombolian activity in summit crater (updated 5 Aug 2013)
Tangkubanparahu (West Java): occasional phreatic explosions (updated 15 Oct 2013)
Turrialba (Costa Rica): ash venting, strong degassing (updated 24 Jul 2013)
Ulawun (New Britain, Papua New Guinea): degassing, ash venting (updated 5 Dec 2013)