Blindly following http://wiki.apache.org/cassandra/CassandraCli, and can someone please explain this?
aaron-mac:apache-cassandra-1.0.0 aaron$ bin/cassandra-cli
set User['jsmith'][utf8('first')] = utf8('John');
If you're unsure about the set command you can type help set; and it'll show the full documentation.
set
help set;