Single Point Injection, automotive

Sisters of Perpetual Indulgence, international non-profit organization raising money for AIDS projects and community organizations, and espousing safer sex

St. Paul's Institution, Seremban, a secondary school in Malaysia

Swiss Precision Instruments, Inc., a supplier of metalworking and metrological instruments, tools, and materials

Survivor Pearl Islands, the 7th installment of the american reality show.

SCSI Parallel Interface

Serial Peripheral Interface Bus, electronics

Simulations Publications Inc., a defunct board wargame company

South Padre Island, Texas, a popular island in Texas

Stateful Packet Inspection (computer networking)

System Packet Interface, a family of interfaces from the Optical Internetworking Forum

State education agency (Office of Superintendent of Public Instruction), American state-level government agencies

IATA airport code for Abraham Lincoln Capital Airport in Springfield, Illinois

Single Page Interface (see Single Page Application)

Sony Pictures Imageworks, a renowned visual effects and animation company

Software in the Public Interest

Swiss Performance Index, a stock index

Sveriges Pensionärers Intresseparti, a Swedish political party

Service Package Interpreter, software

Security Parameter Index, networking

Society of the Plastics Industry, a trade association

Society for Philosophical Inquiry

SPI 200 futures contract, a financial instrument based on the Australian stock exchange.

Service Provider Interface, software

Software in the Public Interest, Inc., the legal representative of Debian and several other Free Software projects.

SPi, A wholly-owned subsidiary of PLDT under ePLDT Ventus

Software Patent Institute, a non-profit organization providing prior art in the field of software technology