RePEc is just a way to organize bibliographic data. A RePEc service uses that data and makes it usable to the public. As the data is in the public domain, anybody can start such a service and make RePEc even more useful. Here is a list of known RePEc services, listed in alphabetical order.
CitEc
CitEc performs citations analysis on works listed in RePEc and returns citation data to RePEc services. CitEc is managed by Jose Manuel Barrueco Cruz and is hosted by the Technical University of Valencia, Spain.
EconLit
EconLit is a bibliographic database sold by the American Economics Association. It also display select working papers series from RePEc. In exchange, Econlit provides some bibliographic metadata to RePEc and support in encouraging more working paper series to be listed in RePEc.
EconPapers
EconPapers displays all the data collected in RePEc, including author information and links to references. The site can be browsed by series, journals, authors and fields. EconPapers also provides various checks to others services and to archive maintainers (metadata syntax, URL checks, linking different versions of the same work). EconPapers is maintained by Sune Karlsson and hosted by the University of Orebrö, Sweden.
IDEAS
IDEAS displays all the data collected in RePEc, including authors information, references, citations, and rankings. The site can be browsed by series, journals, authors, fields, and institutions, or searched. IDEAS is maintained by Christian Zimmermann and hosted at the University of Connecticut, USA.
Inomics
Inomics is a website that was created by the late Thorsten Wichmann. One feature of Inomics is displaying RePEc data. While the rest on the site is continually maintained by Berlecon staff, the RePEc part still runs unmodified after many years. Inomics is based in Berlin, Germany.
LogEc
LogEc performs statistical analysis for downloads and abstract views on select RePEc services (i.e., those that make the effort to provide relevant data): EconPapers, IDEAS, NEP and Socionet. The results can be called in all sorts of ways. LogEc is maintained by Sune Karlsson and hosted by the University of Orebrö, Sweden.
NEP
NEP (New Economics Papers) disseminates new working papers through field specific email lists. At this writing, 83 mailing lists are available, and they typically send a message once a week. To be listed, a working paper needs to be recent, available online, and selected by an editor aided by an expert system. Subscriptions are free. NEP is lead by Marco Novarese, maintained by Thomas Krichel and hosted by SUNY-Oswego, USA.
RePEc Author Service
The RePEc Author Service allow authors to compile all their works listed in RePEc into one folder. Along with contact information and affiliations, the collected data can then be used by other RePEc services, to enrich the displayed data, generate cross-links or compute rankings. The RePEc Author Service is maintained by Christian Zimmermann and hosted by the University of Connecticut, USA.
Socionet
Socionet is a website in Russian that serves a lot of information about research in social sciences, including RePEc data. It also includes RePEc data in Cyrillic that other services typically do not display. Socionet is maintained by Sergei Parinov and Viktor Lyapounov and hosted by the Russian Academy of Sciences in Novosibirsk.
Others
RePEc data is also disseminated through an OAI-PMH portal (OAI=Open Archives Initiative) where it is picked up by numerous other services, including OAIster, Google Scholar and Yahoo Search.
The RePEc Blog 
[…] Publishers provide all the relevant information, which is then displayed in various ways by RePEc services. This allows users to have access to this data. While it is useful to find items of research while […]