SQLcl is the new command line tool from Oracle, more specifically from the SQL Developer team. It is currently an Early Adopter (EA) release and you can download it from: http://www.oracle.com/technetwork/developer-tools/sql-developer/downloads/sqldev-41ea-2372780.html
After testing it for a while I was hooked and plan on using it as a full time replacement for SQL*Plus (which I think is the intent of the product).
The only difficulty I had was where to store it on OS X so it was accessible everywhere. Here's how I "installed" it and hopefully this will be useful for others:
#Note: version/filename of file will change for each release
#Assuming you already have an /oracle directory (I had one for the instant client)
cp -r sqlcl /oracle
#Give sqlcl execute permission
chmod 755 sql
#rename to sqlcl so no confusion (optional)
mv sql sqlcl
#Add directory to path so can run anywhere in the command line:
#Note: See Barry's comment below about storing in /etc/paths.d on Mac
#Add just above the export PATH line
In the above example I installed SQLcl in the
/oracle directory. You could also put it anywhere you want such as
/usr/local/oracle etc. Just make sure that you reference the location in the
PATH environment variable.
Update: The following article covers how to create login scripts for SQLcl.