Since its formal founding 16 years ago, RePEc has grown into a large collection of various services. Users are aware of some, but not all of them. This is an attempt to collect all services that use RePEc data. RePEc is in fact just a way of organizing and collection bibliographic data in economics. Publishers index their works and put it in the public domain through RePEc. Service then use this data in various ways, in part by enhancing it. All linked services are completely free to users and managed by volunteers.
Browsing and searching the database
These are the most basic functions you would want to do with a bibliographic database. Several services provide this. The most popular are IDEAS and EconPapers. Others include Economists Online and Socionet. What distinguishes these services is that they report usage statistics (see below). Yet others that use RePEc include: EconLit, EconStor, Google Scholar, Inomics, Microsoft Academic Search, OAISter/WORLDCAT, Scirus and Sciverse. Shop around and use the one that is the most to your liking!
Curated material
While most the services above provide the complete RePEc bibliographic data, it is the user who has to sift through the material to find what she needs. A few services act as facilitators by helping users with the help of editors who sort and curate the material. NEP disseminates through email and RSS feeds the latest working papers across over 90 fields. The new RePEc Biblio determines the 10-20 most relevant papers in a growing number of fields and sub-fields. EconAcademics.org identifies economic research currently being discussed in blogs.
Specifically for authors
Some services are especially geared towards authors. The RePEc Author Service allows them to create a portfolio of all the works listed in RePEc. Other services then can link from the works to the profiles, and authors can get statistics and new citation notifications. CollEc analyses co-authorship networks and allows, for example, to find how many steps removed from each other any two authors are. The RePEc Genealogy allows to see who graduated where and when and who was the advisor. Finally, the RePEc Plagiarism Committee handles potential plagiarism cases and votes on them, in particular whether to name and shame offending authors.
Statistics
Several RePEc services report traffic on their website, which allows to compute a host of statistics, which are displayed at LogEc. Those, along with citation numbers, allow to compute a large number of rankings of authors, institutions, and papers, including impact factors for serials.
And more
As already mentioned, there is a citation analysis project, CitEc, which uses complex algorithms to extracts references from pdf files and match them with RePEc content.
MyIDEAS allows a user to track other authors, JEL codes, journals or working papers series, as well as build a personal bibliography while browsing on IDEAS. The Socionet Personal Zone also provides some of these functionalities.
EDIRC is a directory of economics institutions with plenty of links to affiliated authors and alumni, as well as compilations of their publications.
Finally, for those authors who do not have the benefit of their local institution participating in RePEc with its publications (see instructions), the Munich Personal RePEc Archive (MPRA) allows them to upload their papers to be included in RePEc.
Posted by Ekkehart Schlicht 
The RePEc Blog 