Types of spanning tree protocols

SPT (802.1d) - the original, good ol' Spanning Tree
PVST+ - Cisco per-VLAN SPT
RSTP -(802.1w) - Rapid Spanning Tree
RPVST+ - Cisco per-VLAN RSTP
MST - RSTP on multiple VLAN instances (do not need SPT per VLAN, groups similar topologies)

Nice summary of the differences between 802.1d (Spanning Tree Protocol - STP) and 802.1w (Rapid Spanning Tree Protocol - RSTP):
http://cciethebeginning.wordpress.com/2008/11/20/differences-between-stp-and-rstp/