One of the great things about the modern AFOL hobby is the abundance of online resources, be it building instructions, brick databases, catalogs, marketplaces or even computer aided design tools, it’s all there. There is also a plethora of LEGO blogs, forums and online stores. Naturally most of this content is easiest accessed through common search engines, but once you start to specialize a little, it does well to understand what the most common AFOL services are.

Online LEGO repositories

These are, to the best of my knowledge, the main repositories for LEGO set and parts information:

  • BrickLink is Internet’s number one marketplace for trading LEGO, new and used. Search “Items For Sale” and you’ll find even the most obscure LEGO sets and parts on sale, search for “Store Name” and you’ll find individuals and outlets selling LEGO. But that’s not all BrickLink is, it is also a premier LEGO sets and parts database. Switch the search to “Catalog Items” and you’ll be looking at the entire LEGO inventory instead. There is also, of course, the “My Wanted List” option for matching buyers and sellers. And because money changes hands with the help of BrickLink, crowdsourcing keeps the database well up-to-date.
     
  • Brickset is another well-maintained site, serving as a sort of an interactive online catalog of most LEGO sets and gear ever made. Brickset is a little sporadic going way back to the early days of LEGO, but it is still my number one stop when looking for basic LEGO set details – readers of the blog may have noticed I link to Brickset a lot and I use it even more when researching the articles. In addition to a set database, organized by theme and year, Brickset also hosts set reviews, link lists and a Brick and Pieces magazine archive (1975-1988).
     
  • Peeron is my go to site for LEGO set parts lists and building instructions. While BrickLink serves much of the same purpose, especially as far as the part database goes, I like the fact that Peeron can be accessed without the sales clutter. Peeron also has a nice “My Parts” feature for collection management. Unfortunately Peeron has fallen into a bit of disrepair lately. While still a formidable database overall, for information on latest sets you may be better off trying e.g. BrickLink.
     
  • LUGNET is another popular LEGO set and part database, from the International LEGO Users Group Network. LUGNET guide is linked to by BrickLink, Brickset and Peeron. In my experience LUGNET is plagued by the same maintenance challenges as Peeron though, not necessarily very up to date, but it does have an interesting ranking system for LEGO sets.
     
  • LEGO Customer Service is useful for only the latest of sets, but does serve a selection of building instructions and replacement parts.

There are also some other, potentially very useful online LEGO repositories:

  • Worldbricks has an extensive archive of old LEGO catalogs as well as building instructions. Worldbricks also has one the most modern interfaces of the LEGO repositories, it even serves stop-motion building videos next to some building instructions.
     
  • Rebrickable, Bricker and the German Brick-sets are also linked to quite often. There is also a site called bricks.argz.com. Depending on the set, these sites can offer additional content not found on the better established sites. Maybe check them out. (Tip: Siabur noted that Rebrickable has useful functionality for seeing what other models you can build with your existing sets/parts.)
     
  • LDraw, started by the late James Jessiman, and various L-CAD efforts maintain a 3D library of LEGO parts and software for designing MOCs on computers. (TLG also has an official alternative called LEGO Digital Designer.)