  Superstring theory has continued to develop at a rapid clip in the past few
years. Following a quick review of some of the major discoveries prior to 1998,
this talk focuses on a few of the more recent developments. The topics I have
chosen to present are 1) the use of K-theory to classify conserved charges
carried by D-branes; 2) tachyon condensation on unstable D-brane systems; and
3) an introduction to noncommutative field theories and their solitons.
