WorldCat can simultaneously search the collections and services of more than 10,000 libraries worldwide. It claims to be the largest network of library content and services. Users can search for resources available in their community and also at thousands of other locations all around the world. It helps you finc the item you are looking for and the library near you where the item can be found.

Library Lookup is a bookmarklet that can look up whether a book is available in the user's local library, based on information about that book on a separate website (e.g. Amazon). Supported library systems are listed here.

Google Books provides full, free PDF scans (and web-viewable versions) of public domain books and magazines, free previews of some books and magazines under copyright, and the option to purchase digital editions of available items to save and read on Google Play, their e-reading platform. You can also find a local library based on your zip code that has the item available. Reader reviews of the items are available and you can contribute your own. Search for authors, titles, as well as keywords and Google will return results with matches in the title/text of the item. There are permalinks to available pages. Highly useful for finding items that contain your keywords in its text.

It has the Google Ngram Viewer as part of its service. The Ngram Viewer is a service connected to Google Books that graphs the frequency of word usage across their book collection

LibLime's Koha is a web-based, open source integrated library system (ILS) that has also been used for virtual library systems (e.g. recreating historic libraries). LibLime Koha offers libraries circulation policies, patron management modules, parent-child relationship for patron records, club and service management features, in-depth "holds" support, single click batch import "undo" option, EzProxy compatibility, self-checkout interface and more.

AGTK is a suite of software components for building tools for annotating linguistic signals, time-series data which documents any kind of linguistic behavior (e.g. audio, video). The internal data structures are based on annotation graphs. Annotation Graphs are a formal framework for representing linguistic annotations of time series data.

(Note: last release 2007. Last update on sourceforge page 2011). The links on the sourceforge page are broken: software is reportedly released under a 'Common Public Licence', although the link to the licence at http://www.opensource.org/ is broken; link to the project website at the Linguistic Data Consortium is broken.

Mapstraction is a Javascript library. It provides developers with a single interface for a wide variety of Javascript map APIs including Leaflet, Google, Bing, OpenLayers and ESRI's ArcGIS.

A key benefit is that once a developer has loaded Mapstraction, s/he can to switch from one map API to another quickly and easily - often only needing to change a few lines of code.

Mapstraction displays points, lines, polygons and markers on the maps, and also allows developers to add base maps and overlays.