One of my favourite Joomla companies has come up with a great idea: ask everyone what thier essential extensions are for Joomla. My number one extension is the JCE wysiwyg editor, I use it as standard on all my clients sites. I'm not sure what I'd do without it. In fact I'm using it right now to write this post.
Compass Designs wrote the tutorials I used to learn how to build templates for Joomla, I feel indebted to them for that and so here is an announcement direct from them:
Announcing the Ultimate Top 10 Joomla Extension competition sponsored by Joomlashack.
"What are your favorite Joomla extensions?"
You might have heard of UserVoice. Its a great web 2.0 application where people can vote on things. Everyone gets a set number of votes, in this case 10. You guessed it, we are going to ask you to vote on what you think are your "bread and butter" extensions. You can give one extension all your votes, or spread them around.
The only guideline is vote for extensions you "couldn't do without". Also, make sure you search for an extension before you vote, we don't want to dilate votes, and feel free to make enthusiastic comments! If you suggest an extension, try to enter the title as the name of the extension that appears on the extension directory.
You can vote for your top 10 extensions here.
Just to make it a little more fun, Joomlashack is giving out some prizes. In one month's time (May 7th), the #1 extension gets a $200 prize, and #2 $100.
Feel free to promote the competition with our handy announcement html
Come on and join in the fun, and here is a glimpse at the current top 3 extensions!

My other favs are NinjaXplorer, JoomlaPack, Teamlog. I have a forum post on our website with our top extensiond for Joomla. View it here:
http://pixelpointcreative.com/support/forum.html?func=view&catid=16&id=50