Nano is a GNU project that is an enhanced version of pico, which retains its easy-to-use interface with some very useful features- including find-and-replace, go to a specific line number (both very useful for programming), justify text, continuous display of cursor position (line number and character number), case-sensitive-search, tab-completion when saving or reading, etc. Also, common functions are now mapped to the Fx function keys, F1 is help, F2 is quit, F7 and F8 scroll the page up and down, F9 and F10 cuts and pastes the current line, etc. The current unstable development versions allow color syntax highlighting and support for multiple file-buffers.
Note: Some features use the meta-key which doesn't exist on mac keyboards, so you will need to press the escape key then the desired letter when accessing some features, for example escape the 'c' for constant display of cursor position.
To install pico, download the source from the Nano homepage, then navigate to the source directory and type
%./configure[Editor's note: I downloaded the 1.09.tgz source (444K download), and it compiled and ran perfectly. Looks like a nice pico replacement!]
% make
% sudo make install

