what has happened to mount Pinatubo between the eruption in 1991 and today?

Question

What website would I find this info in?

Answer 1

http://www.volcano.si.edu/Reports/usgs/index.cfm?content=archive&volcano=pinatubo
The website above, by the Smithsonian and the USGS, contains updates of geologic activity around Pinatubo since the eruption.
Widespread lahars (volcanic mudflows) that redistributed products of the 1991 eruption have continued to cause severe disruption. In 2001, there was such a major concern over rising water levels in the crater lake that an effort was made to drain it somewhat. Then, On 10 July the western wall of Pinatubo's crater collapsed, gradually releasing about 160 million m3 of water and sediments. The collapse occurred at the crater wall's lowest point leading to the Maraunot River in Botolan, Zambales. About a year earlier workers had removed a section of the crater wall in an effort to gradually release the rapidly rising water in the crater and prevent a larger crater-wall collapse. PHIVOLCS reported to Philstar news that if the notch had not been created at least 320 million m3 of water and sediment could have been released into inhabited areas.
In 2004, tourists noticed that the usually blue-to-green water in Pinatubo's crater lake was very dark brown. Scientists from the Pinatubo Volcano Observatory excluded renewed volcanism as the source of the discoloration due to the lack of increased seismicity, and an absence of new emissions in the crater or any increase in the water's temperature. They believed the change in water color was due to near-surface processes, such as biogenic activity or a steady supply of nutrient rich soil from landslides that have entered the crater since its formation after the June 1991 eruption. Visitors were warned against swimming in or consuming the water in the lake.

Answer 2

Nothing, barring plasma emmission. It has remained dormant ever since.