The past year i wrote an article about must have Firefox 3.6 compatible extensions, the post still remain valid (many extensions are updated with new browser versions), with the new Firefox 4 version here is a nice collection of new (or updated) extensions to have:
Always right allows to open new tabs immediately to right
Blue Box Proxy it allows to bypass sites with restrictions
Cloud Magicintroduces instant search for your online data
Cocoon privacy extension to surf safe
Cookies Manager+ it allows to modify the cookies
DeeperWeb it allows to surf to Google results with like tags
Do Not Track Plus another privacy extension
Download Youtube Videos + it allows to easily dowload Youtube videos and from other many sites
Drag2Up it makes easy file hosting uploads
F1 Mozilla extension that allows you to share links in a fast and fun way
Fireshot extension to make screenshots
Flash Video Downloader it allows to download Flash videos from many sites
FlashResizer it allows to resize Flash windows
FloatNotes it allows to add useful notes
HTTPS finder it allows to surf with https when available
GrooveControl an extension that interfaces with Grooveshark service to listen music
MinUI it allows to modify the browser GUI
Home Dash an high customized dashboard
People Lookup it allows to find peoples info
PlayLink redirect links to an external media player
Power Twitter add many features to Twitter
RSFind it allows to find on file hosting sites
Start Faster it allows to start Firefox more fast
Tab Badge notifies about site updates on tabs
TabCloud it allows to save opened tabs on the cloud
Textarea Cache it allows to recover lost text of web forms
TooManyTabs allows you to store as many tabs as you like by adding extra rows
TrashMail it allows to create temporary email inboxes
TwitterBar it allows to tweet from browser address bar
Update Scanner monitor web pages and notifies updates
vertical tabs it makes a vertical layout of the tabs
ViewMarks it allows to save bookmarks in an alternate way
Youtube Music Player a music player for the famous site
You can download all in a single pack here (inside there are all the extension urls)
