PropForth is a fully interactive development environment which runs on the Parallax Propeller allowing you to program the chip interactively in Forth using a PC serial terminal program. Their latest code release is Version 4.5.
According to their project description:
Propforth 4.5 introduces standardized interfaces (cog, serial, ethernet, etc), SD support (thanks caskaz), completed EEPROM filesystem support, forth code scripting (files that are loaded and interpreted as scripts that do not need to affect the dictionary), and Spinneret webserver support. The Spinneret support includes telnet, http, NTP, and RTC.