Omseek has been renamed to Xapian. Xapian is a Search Engine Library, written in C++ with bindings for Perl, Python, PHP, Java, Tcl, C# and Ruby. It allows you to easily add advanced indexing and search facilities to your applications. See xapian.org
pyChelsea is a python based, personal, visited, web page indexer, seach engine and interface for the browser/platform of your choice. If you remember a page based on a phrase, pyChelsea is for you.