This is the best list of search enignes:

AskMeNow: S3 - Semantic Search Solution

Concept Searching Limited: concept search products

Dieselpoint: Search & Navigation

dtSearch: dtSearch Engine(SDK), dtSearch Web

Endeca: Information Access Platform

Exalead: exalead one:enterprise

Expert System S.p.A.: Cogito

Fast Search & Transfer: Enterprise Search Platform (ESP), RetrievalWare (formerly Convera)

Funnelback: Funnelback Search

Jumper 2.0: Universal search powered by Enterprise bookmarking

ISYS Search Software: ISYS:web, ISYS:sdk

Microsoft: SharePoint Search Services

Northern Light

Open Text: Hummingbird Search Server, Livelink Search

Oracle Corporation: Secure Enterprise Search 10g

SAP: TREX

TeraText: TeraText Suite

Vivisimo: Vivisimo Clustering Engine

X1 Technologies : X1 Enterprise Search

ZyLAB Technologies: ZyIMAGE Information Access Platform