Google Scholar Subject Area: General, Multi-Subject

Google Scholar provides a simple way to broadly search for scholarly literature. From one place, you can search across many disciplines and sources: peer-reviewed papers, theses, books, abstracts and articles, from academic publishers, professional societies, preprint repositories, universities and other scholarly organizations. Google Scholar helps you identify the most relevant research across the world of scholarly research. (Provides fulltext access to various resources)

OAIster : Union Catalog of Digital Resources   Subject Area: General, Multi-Subject

OAIster is  a huge union catalog of digital resources.  

BASE:Biefeld Academic Search Engine    Subject Area: General, Multi-Subject

BASE is the name of the multi-disciplinary search engine for academically relevant web resources which was created and developed by Bielefeld University Library.

The Virtual Library    Subject Area: General, Multi-Subject

The Virtual Library is a catalogue of the web.

USA Government Science Portal  Subject Area: General, Multi-Subject is a gateway to government science information and research results.

Find Article in BNET   Subject Area: General, Multi-Subject

Offers academic full text documents in the fields of Science and various fields

Dogpile      Subject Area: General, Multi-Subject

All the best search engines piled into one.

The Internet Public Library       Subject Area: General, Multi-Subject

DMOZ Open Directory Project     Subject Area: General, Multi-Subject

The Open Directory Project is a human-edited directory of the Web. It is constructed and maintained by a vast, global community of volunteer editors.

TechXtra Subject Area: Engineering + Mathematics  

Find articles, key websites, books, the latest industry news, job announcements, e-journals, e-prints, technical reports, the latest research, thesis and dissertations and more.

Scirus : For Scientific Information Only Subject Area: Science  

Scirus is the most comprehensive scientific research tool on the web. With over 350 million scientific items indexed at last count, it allows researchers to search for not only journal content but also

scientists’ homepages, courseware, pre-print server material, patents and institutional repository and website information.

Athenus : The Engineering and Science Search Engine  Subject Area: Science + Engineering