Taal Volcano is one of the more active volcanoes in the Philippines, distinguished by its close proximity to heavily populated and industrialized areas, which makes it a major risk to residents.
Taal is located 50 km (30 miles) south of Metro Manila (about an hour's drive) on the island of Luzon, and is thus a favorite tourist attraction (the view from the Tagaytay Ridge, overlooking the caldera lake, is unmatched). At night, you can usually see the faintly luminous ash clouds drift overhead. I'd recommend the Taal Vista Lodge - while you can get a guide, there's free access to a meadow right on the Ridge with a good view.
The Taal volcanic system consists of a 30 km-wide crater lake (Taal Lake), with a low-profile pre-caldera cone (Volcano Island, or Taal Island) in the middle. It can't really be called Mount Taal, since most of the Tagaytay Ridge is higher than the cone itself.
Over 34 major eruptions have been recorded since 1572, usually limited to Volcano Island and the lake region, but at least two in recent years have forced evacuation of villages and towns to the west. Historically, earthquakes and ash fall generated by Taal's eruptions have reached as far north as Manila, but no large eruptions have been reported since 1965.
Taal Island is legally off-limits to anybody but vulcanologists, but some farmers have set up homesteads on it (due to the extremely rich soil). The area in the immediate vicinity, Tagaytay, consists of light industrial parks, country clubs, and high- and middle-class housing; a major eruption in the near future may cause severe damage to millions of pesos worth of property. The Philippine Institute of Volcanology and Seismology (PHILVOLCS) has designated it one of fifteen Decade Volcanoes, out of over 200 found in the country, slated for priority observation and monitoring, although the recent Pinatubo eruption has pulled resources away from Taal.
Most facts taken from http://www.iml.rwth-aachen.de/Petrographie/taal.html and http://volcano.und.nodak.edu/vwdocs/volc_images/img_taal1.html.