TyRaNiD over at ps2dev.org has released a new version of PSPLINK. For those that have never heard of it before it is a loader/development tool for homebrew developers for 1.0 and 1.5 firmware only (sorry no 2.0+). It provides you with a shell which you control on your psp to load new applications over USB or from Memory stick then quickly reset and start over again. It comes with SIO (i.e. Remote Control Serial port), WIFI, USB and Console shells, has a USB host filing system to access executables directly on the PC and has a GDB server for source level debugging. Other features include the ability to inspect most of the system in realtime (such as threads or loaded modules), dump memory contents, disassemble instructions, print text to the PC using printf and even take screenshots.
Read the included manual to understand how to setup and operate the tool.