CGIwithR - Package to use R as CGI script language. Uses: online calculators, with R as compute engine; processing web forms generally, with R as alternative to more common script languages, e.g., Perl.
Rpad - Interactive, web-based analysis package, webpage and GUI designer. Pages are workbook type sheets in R. Makes data analysis programs that share with others easily, via web browsers. Descriptions, documents, downloads. [Open Source, GPL]
R-php - Coded in PHP and MySQL, to run requires: PHP, MySQL, Apache, ImageMagick, Netpbm. Downloads.
Rserve - TCP/IP server for other programs to use R from various languages with no need to initialize R or link to R library. Each connection has unique workspace, working directory. Client implementations for common languages (C/C++, Java). Remote connection, authentication, file transfer. Descriptions, documents, downloads.
Rweb - Web based interface to R, takes submitted code, runs R on it (batch mode), returns the output (printed or graphical). Set up your own Rweb server by downloading source code and support software. Descriptions, documents, downloads.