[Edit]

"It's" man, a man with torn clothes and unkempt beard who appeared at the beginning of episodes of Monty Python's Flying Circus

International Tracing Service

"its", a possessive pronoun

"it's", a contraction of "it is"

Computing

iTunes Store, an online music service run by Apple Computer through its iTunes application

Incompatible Timesharing System, a computer operating system

Internet technical support, the people you call to repair your Internet connection

Intelligent tutoring system, an artificial intelligence system used for tutoring

Issue tracking system, computer software packages that manage and maintain lists of issues, as needed by an organization

Information Technology Services, a generic name for a computer support department

SAP Internet Transaction Server

Education

Institute of Technology, Sligo, Ireland

Institut Teknologi Sepuluh Nopember, in Surabaya, Indonesia

Intelligent tutoring system, an artificial intelligence system used for tutoring

Science and engineering

ITS-90, or International Temperature Scale, which provides the defining points for temperature

Internal transcribed spacer, a section of DNA located within a set of ribosomal genes

Intelligent transportation system, using technology to improve the efficiency of roads

Organizations

Islamic Thinkers Society

International Thespian Society, an honorary organization for high school and middle school theatre students

Art

International Typographic Style, a graphic design style developed in Switzerland in the 1950s