This article presents extensions that I successfully used in different projects and that I highly recommend.

Google

•  mono_ga: Google Analytics support
•  dd_googlesitemap: Generation of sitemaps

Gallery

•  chgallery
  •  perfectlightbox: Lightbox support
  •  metadata_ts: Adding EXIF/IPTC support

Security

•  naw_securedl: Protect files in fileadmin and other directories

Misc

•  fhm_author: Save current author name and email as most recent page author
•  rgfolderselector: Easily select directories in backend using a browser