Quest Software's TOAD (Tool for Oracle Application Developers) has evolved a long way since it's first release, and is now a tool for far more than just an application developer.
I'm going to focus this review on the Oracle version of Toad. There are other versions available, but I've never used them, so I can't comment...
Before installing Toad, you must already have an Oracle client installation on the PC - the Oracle server doesn't have to be on the same machine (but you'll need one somewhere... otherwise why are you using Toad?).
Unlike other similar applications though, you won't need to have pre-configured your TNSNAMES file with details of the databases you'll be connecting to - Toad provides a very easy to use TNSNames editor in the login window.
When Toad starts, you are greeted by the trademark croak (which can of course be turned off), and presented with a list of your recent connections. These can be sorted, searched, and filtered; you can also choose whether or not to save passwords for even faster login. This feature alone is invaluable for people who must often connect to different databases.
The initial view on entering Toad is a fairly simple SQL entry window. This view allows you to enter any valid SQL commands or PL/SQL scripts for execution. Display of the results is in a very convenient scrollable & resizeable table in the bottom half of the window.
The next most useful view is the Database Schema Browser. This lets you view (and modify) tables, views, packages, procedures - in fact, any of the Oracle database objects you can name. All objects are displayed in a convenient manner - for tables, you can browse the table definition, the data, or even the statistics; for packages and procedures you can view the source; for views you can see the source query, the data and the structure as required.
As well as this there are numerous utilities; a data file browser that lets you see the capacity, size and growth parameters for all your datafiles; a tablespace manager that lets you view the contents of a tablespace and check for fragmentation; a session browser that can examine the queries being run by any session you have access to... I could go on...
There are two problems with Toad. The first is the price, which is prohibitive. You'll be hard pushed to make a business case for Toad where it recoups it's cost in less than a couple of years - especially if you have multiple users, and especially compared to cheaper alternatives.
The second is reliability. While using Toad, I have experienced multiple crashes and lock-ups. These are usually the result of a long-running query blocking the Toad user interface, but in a tool like this, queries should run in a thread safe manner by default!