  We show that the relation between D-branes and noncommutative tachyons leads
very naturally to the relation between D-branes and K-theory. We also discuss
some relations between D-branes and K-homology, provide a noncommutative
generalization of the ABS construction, and give a simple physical
interpretation of Bott periodicity. In addition, a framework for constructing
Neveu-Schwarz fivebranes as noncommutative solitons is proposed.
