Although it is not a new architecture, for those interested in having a hands-on experience setting up and running an IR system, a good choice is UNESCO’s CDS/ISIS platform.
According to the pdf documentation,
CDS/ISIS is a menu-driven generalized Information Storage and Retrieval system designed specifically for the computerized management of structured non-numerical data bases. One of the major advantages offered by the generalized design of the system is that CDS/ISIS is able to manipulate an unlimited number of data bases each of which may consist of completely different data elements. Although some features of CDS/ISIS require knowledge of and experience with computerized information systems, once an application has been designed the system may be used by persons having had little or no prior computer experience.
Another toy to play with during 2009.
PS. I changed title to “free text searching” for accuracy.