Custom Content (CC) are custom items that are made from other players and added to the game, in The Sims 3 it includes other create a sim/create a pet itens, buy and build mode items, pose packs, custom worlds and mods. These are my bookmarked CC links.

Bigger websites & updates websites:

• Around the sims 3
  Famous big website that focuses on thematic CC
• Hair's retexture catalogue
  A google docs list with hair retextures (I can't remember who is the creator)
• Modthesims
  Famous website + forum with tons of stuff
• My Sims 3 blog (inactive)
  Sims 3 CC updates blog
• nraas mods
  Famous wikia + forum of essential mods
• OneEuroMutt Master Slider's List
  A big list with tons of sliders
• Sims 3 Updates (inactive)
  Sims 3 CC updates blog

Themed sites:

• Cheshire farms (inactive)
  Website with CC and worlds equestrian themed
• Historical finds for TS3
  CC finds blog history themed
• Home grown (inactive)
  Website with CAS and Buy mode CC with pregnancy, babies and kids theme
• Itsyuiri
  The Sims Medieval conversions
• Pregger sims (inactive)
  CC finds blog with a maternity/baby theme
• Sims 3 Anime finds (archived)
  CC finds blog with a anime theme
• Sims 3 Edit (inactive)
  CC finds blog that specializes in Maxis content edited
• Sims 3 Medieval
  Blog about making TS3 medieval, has some tips and downloads
• The Sims 3 medieval finds (inactive)
  CC finds blog medieval themed

Sites & blogs:

• B5studio (inactive)
  Website with mostly Buy mode CC
• David Montenegro (inactive)
  Blog with mostly Buy mode CC
• Helen sims (inactive)
  Blog that features mostly Buy mode CC
• Ladesire The Sims 3 (inactive)
  Blog with both CAS and Buy mode items
• Latoya sims (inactive)
  Blog with both CAS, Buy mode and Build mode items
• Lorandia Sims3 (inactive)
  Website featuring CAS CC
• Madness of Kanoya (inactive)
  Blog featuring CAS CC
• More than just pixels (inactive)
  Mostly mods
• Navetsea (inactive)
  Blog featuring CC skins
• One billion pixels (inactive)
  Blog featuring mostly Buy mode CC
• Silver Moon Sims 3 (inactive)
  Blog featuring CAS CC (mostly Sailor Moon themed)
• Simmerstore (inactive)
  Blog that features CAS CC
• Simple life (inactive)
  Website that features CAS CC
• Sketchbook pixels
  Website that features CAS CC
• Tifa Sims
  Blog that features CAS CC

Simblrs:

• Akikka88 (inactive)
• Amethyst sims (inactive)
• Ani's Sims
• Antraya cubed (inactive)
• Awesome sims (inactive)
• Beaverhausen (inactive)
• Beo Creations (inactive)
• Crowkeeper the simmer
• Divadoom (inactive)
• EÁMANË PALANTÍR (inactive)
• Hello Domo Bear (inactive)
• Ifcasims
• Il Grande Lama CC
• Imamiii
• Jennisims (inactive)
• Juniellie (inactive)
• Kent converts (inactive)
• Koolhira (inactive)
• Leah Lillith (inactive)
• Morgana plays (inactive)
• Mspoodle's Meow
• Murfeelee
• Nigalkins (inactive)
• Nixels (inactive)
• Nockciimii (inactive)
• Nygirlsims (inactive)
• Omfgingers
• Pandelabs
• Potato ballad sims
• Risastorm (inactive)
• Samsimmie's Sims 3
• Simpli Caz (inactive)
• Simply kitab CC finds (inactive)
• Simply kitsch (inactive)
• Sims 3 Legacy CC (inactive)
• Simstiful
• Simstiful CC finds
• Sommerliersims
• Sunny CC finds (inactive)
• Sweetdevil sims
• Teekapoa
• Vkg simblr
• Wicked sims (inactive)

Other:

• Bountiful Berries (inactive)
  Blog with berry sweet sims to download
• Community lot repository (inactive)
  Blog with community lots that fit EA made worlds
• Crinrict's Sims 3 Help Blog (inactive)
  Sims 3 guide blog
• Fake houses real awesome
  Blog with premade houses to download
• How to make your townies look different
  Tutorial to make your game generate diffent townies
• Sims for sale (inactive)
  Blog with sims to download
• Tutorial: Making Sims
  Tutorial to create unique sims