Thanks for the link Richard.

Beware the Journalistic Supervolcano!

http://www.wired.com/wiredscience/2013/02/beware-the-journalistic-supervolcano/.

Eruption at Mt Etna this morning (19 Feb 2013), 

http://earthquake-report.com/2013/02/19/volcano-activity-of-february-19-2013-fountains-of-fire-at-etna-sicily-this-morning/.

Impressive lava fountains from Etna volcano.

http://www.wired.com/wiredscience/2013/02/stunning-lava-fountains-from-italys-etna/.

Another paroxysm at Etna volcano with impressive lava fountains. See:-

http://www.etnanews.com/2013/03/etna-eruption-6-03-2013/.

http://www.youtube.com/watch?v=hRR9Ujrzc7w&feature=player_embedded.



El Hierro is becoming restless again.

http://earthquake-report.com/2011/09/25/el-hierro-canary-islands-spain-volcanic-risk-alert-increased-to-yellow/.

Reports of other volcanoes around the world can be seen here.

http://earthquake-report.com/2013/03/21/volcano-activity-of-march-21-2013/.

Another volcano to watch at the moment is Hekla, of Iceland, which has been showing unusual seismic activity. 

http://www.ruv.is/frett/seismic-activity-in-mount-hekla.

Hekla is prone to sudden eruption. Whether this will happen within days or hours, only time will tell. Here are the webcams so that you could check if anything is happening.

http://www.ruv.is/hekla.

http://www.livefromiceland.is/webcams/hekla/.

Yes indeed, an another +4.0 M earthquake has struck early this morning (4.6 M) and seismic unrest continues vigorously. More about this here,

http://www.volcanodiscovery.com/elhierro/current-activity.html.

The earthquakes can also be seen in this wider map here,

http://www.emsc-csem.org/#2.

The latest news is, at 10:11:06.9, a 4.2 M earthquake.

Keep a close watch on it!

3.2 Magnitude earthquake occurred at Yellowstone.

http://earthquake.usgs.gov/earthquakes/eventpage/uu60017492#summary.

Vigorous seismic activity is occurring just off N coast of Iceland, 

http://en.vedur.is/earthquakes-and-volcanism/earthquakes/

Selection of webcams of Etna volcano here.

http://www.ct.ingv.it/en/webcam-etna-en.html.

Keep an eye on Hekla volcano, which could be close to erupting;

http://theextinctionprotocol.wordpress.com/2013/05/01/hekla-volcano-iceland-strong-inflation-suggest-volcano-could-be-close-to-erupting/.

Latest news of other volcanic activity (also including Hekla) can be seen here;

http://www.volcanodiscovery.com/volcano-activity/news/33170/Volcanic-activity-worldwide-30-Apr-2013-infation-at-Hekla-ongoing-eruptions-at-Tungurahua-and-Fuego.html.

I'm always a bit wary of sites which call themselves 'The Extinction Protocol'; but if Hekla is bulging, it needs watching as this one mother of a volcano when it does let rip!

Mayon volcano in Albay Philippines belched out black smoke on May 7, 2013 @ 8AM. It reached about 3 kms high and still rising. No official report yet from PHIVOLCS Legazpi. Unverified reports of a tourist guide killed and 4 tourist climbers injured.

http://www.youtube.com/watch?v=Daz21tMfSRw&feature=youtu.be

Is there any data or graph available showing multi-decadal/centennial volcanic activity related to numbers and magnitude?

I haven't yet found exactly what you want, but you may be interested in these,

http://www.eh-resources.org/volcanoes.html,

http://chiefio.wordpress.com/2013/05/06/hekla-ing-egypt/,

http://volcanoes.usgs.gov/hazards/gas/climate.php,

http://en.wikipedia.org/wiki/Timetable_of_major_worldwide_volcanic_eruptions.

Popocatepetl volcano of Mexico is quite active at the moment, producing relatively strong explosions. More details here;

http://www.volcanodiscovery.com/popocatepetl/news/33633/Popocatepetl-volcano-Mexico-explosions-eject-bombs-to-15-km-distance.html.

Plus a video to go with it;

http://www.youtube.com/watch?v=gUy7PsYOK1s.

System upgrade for warning of volcanic eruptions in Iceland - see -

http://www.upi.com/Science_News/2013/05/23/Iceland-upgrading-volcano-eruption-warning-system/UPI-95681369340669/

Copahue volcano on Chile/Argentina border is erupting, prompting evacuation,

http://www.bbc.co.uk/news/world-latin-america-22684322.

Sakurajima volcano of Japan produces a spectacular fireworks display (sorry for faulty cameras),

http://www.youtube.com/watch?v=tDkb32l19SI.

More about Sakurajima here,

http://www.volcanodiscovery.com/sakurajima.html.

Nice explosive eruption on Popocatepetl volcano of Mexico today (17/6/2013),

http://www.youtube.com/watch?v=3ATDHCtaMBs&feature=youtu.be&a.