Dropping a group of schemas with similar name patterns
This query on the system catalog creates the necessary DDL script:
SELECT string_agg(format('DROP SCHEMA %I CASCADE;', nspname), E'\n')
FROM   pg_namespace
WHERE  nspname LIKE 'ceu_shard_test_merge_%';

Note the use of format() to escape identifiers if necessary.
format() requires PostgreSQL 9.1+.
Replace with quote_ident() in older versions.
string_agg() requires PostgreSQL 9.0+.
Replace with array_to_string(array_agg(...), E'\n') in older versions.
For Postgres 8.4, that would be:
SELECT array_to_string(
          array_agg('DROP SCHEMA ' || quote_ident(nspname) || ' CASCADE;')
        , E'\n')
FROM ...

Returns:
DROP SCHEMA ceu_shard_test_merge_1 CASCADE;
DROP SCHEMA ceu_shard_test_merge_2 CASCADE;
...

Which you can inspect before executing.
You can put it all into a DO command for automatic execution or create a function for repeated use. Consider this closely related answer for a complete code example:

Bug in PL/pgSQL function creation

Or this related answer on SO.
Output in psql
In response to @Stew's comment: To display unadorned text as result in psql you can use the \pset meta-command:
\pset format unaligned
\pset tuples_only

Or use the short commands \x \a