VTL-02 is a nifty little programming language - 1020 bytes of code gives you something close to Basic. Written in 1976 for the Altair 6800 by Frank McCoy and Gary Shannon, it was only recently ported to the 6502 by Mike, and then tuned by Klaus, on the 6502 forum (link). It counts as one of the top early microcomputer programming achievements.
I was able to wedge it into the KIM Uno's ROM map, so it now boasts not only a machine language monitor and (Wozniak's original) disassembler, but also an easy-to-use interpreted language. Well, easy after you read the manual (here). It does require a serial terminal, or more likely a USB-to-Serial cable to your laptop used as a terminal. Because the on-board hex display really won't cut it :)
One more example of what you can do with less than 1024 bytes of code. And one more vintage 6502 coding gem in the KIM Uno. Thanks, Mike & Klaus!
The KIM UNO Firmware update is here, at the bottom of the page.