Copy few rows from one database to another
Off the top of my head, here are a few ways to do it without resorting to 3rd-party tools.

If you are using PostgreSQL 9.3, you can use the extension postgres_fdw.

If you are using an older version of PostgreSQL have a look at dblink

If you want a command-line only solution, and you are using Linux (or Cygwin etc), you could try something like the following:

psql -d yourdb -qtAXc "COPY (select col1, col2, col3 from your_table where id between 123 and 456) TO STDOUT CSV HEADER" -U youruser -h localhost -p 5432 \
| psql -d yourremotedb -U youruser -h your_remote_host -qtAXc "COPY yourtable FROM STDIN CSV HEADER"