There are many options for editing and writing Stored Procedures in Oracle; what is the best tool for you and why? (one tool per answer.)
Tool for Oracle Application Developers (TOAD), from Quest Software (formerly TOADSoft) has an excellent Stored Procedure editor with syntax highlighting, some autocomplete support (e.g. type in 'TABLE.
' and the columns will appear), a nice Execute Procedure option that will show the results in a Grid or show DBMS output, and will also focus on syntax errors when you hit compile.
Note: The Freeware edition only allows 2 concurrent connections to the same Database Instance (even though the website says 5) - that means only 2 developers or DBA's can use it at the same time on the same Database. It also expires every 3 months but they're good at releasing updates.