AKEEBA BACKUP
If you are looking for a powerful yet simple extension for keeping a backup of your Joomla! site, Akeeba Backup, the best (IMHO) open-source backup component, was created for you! Created to handle big sites and avoid server timeout. It creates a backup archive that contains all the files, a database snapshot and a restoration point.
Akeeba Backup comes in two versions that are called Core and Professional. Core version is free (Non-Commercial), provides some basic backup tools and an unlimited service. This is the version that IDEAS install in all Joomla that we install. But for more advanced options, you can try the Professional edition for a small fee. Always backup - backup - backup.
NINJA XPLORER
Have you ever tried to work through FTP and Joomla just doesn't let you override some of the files? Even with permissions sometimes it's just a nightmare and a full pullhair experience. Well, Ninja Xplorer solves that because is the premiere file system explorer for your J1.5 website. You can edit, upload, delete, zip, unzip and download files directly from your Joomla Administrators panel without the need to go through your FTP. Also it's convinient if you are not on your primarly desktop/laptop and/or you are just using a borrowed computer.
JCE-Joomla Content Editor
JCE is the award-winning WYSIWYG editor plug-in for creating and editing Joomla's contents easily. It has a cool content creating environment with beautiful familiar options to make the user experience better. Add a set of tools to your Joomla!® environment that give you the power to create the kind of content you want, without limitations, and without needing to know or learn HTML, XHTML, CSS... Moreover, it is free and extendable with different additional plugins. It can also be customizable in some extent.