This outstanding web site, supported to the is a center for worldwide holocene volcano and eruption information. You can search the volcanoes of the world by region (interactive map), name (search by name or browse world list), and eruption date.
It includes links to activity reports (weekly & monthly), atmospheric effects, additional reports, special announcements, and photo galleries of types of volcanoes & their processes. Many volcanoes have photos with detailed information about them (e.g. Mount Hood, OR).
The GVP supports an increadible dynamic planet map that lists volcanoes, earthquakes, impact craters, and plate tectonics all combined into one resource. It shows Earth's most prominent features from a distance, but also zooms into detailed features for closer inspection. It provides text, timelines, references, and other resources to enhance understanding of this dynamic planet. The main and polar maps are interactive, and allow users to make their own regional map with existing layers. Data for any volcano, earthquake, or impact symbol can be found via the "Identify" tool.
There is also a downloadable Google Earth Placemarks & descriptions tool for people to include in their own Google Earth maps. The site lists its data sources, and links to official observatories & official agencies according to region.
The USGS CVO site contains a variety of maps, historical information & descriptions from potential active volcanoes & volcanics of the Western U.S. and around the world. It has news and current events, activity updates, photos galleries, cascade range volcano listings, hazard assessment reports & maps, hiking information, Mt. Saint Helens 30th anniversary, volcano types, glossary of terms, and even what these volcanoes were like during the 1805 Lewis & Clark expedition.