This page points to external listings as well as providing a place to describe different approaches for converting existing tabular data (spreadsheets and CSV files, mostly) to RDF.
For starters, OpenRefine and its predecessor Google Refine are worth learning, and Eliza from Weill Cornell wrote and has documented a Google Refine plugin for VIVO.
Tim Lebo from RPI maintains a Alternative Tabular to RDF Converters page on Github.
from the public-semweb-lifesci@w3.org list:
Peter Ansell: Michel Dumontier's php-lib library is what Bio2RDF has been using for converting TSV, CSV files (and other file formats) to RDF [1]. It contains some aspects that are Bio2RDF specific, namely its support for prefixed URIs, but any Pull Requests on GitHub would be appreciated to generalise that. OSX has PHP installed by default as far as I know so you can use it on the command line without any other dependencies.
You can find examples of scripts using php-lib in the bio2rdf-scripts repository on GitHub [2]. A fairly simple example would be the HGNC converter, which is Tab separated, but quite similar [3].
[1] https://github.com/micheldumontier/php-lib
[2] https://github.com/bio2rdf/bio2rdf-scripts
[3] https://github.com/bio2rdf/bio2rdf-scripts/blob/master/hgnc/hgnc.php#L129
