Shoebox is a free database program which is popular with linguists for keeping notes and making dictionaries. Currently, although we hope to eventually keep an online database of NGL morphemes, the Shoebox database (and its text counterpart available in Jerry Koenig's Writekit) constructed and maintained by Stephen DeGrace is the only available complete list of the NGL language's accepted morphemes. Fortunately, Shoebox is neither a large program nor one that is difficult to learn how to use. First, download the zipped database files from this site. If you are just doing an update, simply extract the files in the archive to your "My Shoebox Settings" folder, open Shoebox, and under the Projects menu, open the file NGLvocab.prj. If you are installing for the first time, first download Shoebox and install, an elementary and self-explanatory procedure. Then, using the archive, proceed exactly as you would to update.
Please bear in mind that this database a) was only originally intended to serve for personal notes and b) is an imperfect, individual volunteer effort. This would explain any eccentricities or errors you may find. Which is to say that the database is not perfect - it should nevertheless prove a valuable resource. If you find any errors or have any questions at all relating to installation, functioning, or content, please email Stephen DeGrace.
New Addition: I have recently written a small windows utility which can convert the file NGLLex (no file extension), the data file for the Shoebox NGL database, to TDF (Tab Delimited Format, each record on one line, fields separated by tabs characters) format for easy importation into spreadsheet programs. To use, download the conversion utility .zip file, unzip, and run the file NGLxC1_0.exe to install. Then download the database (above) and extract the file NGLLex in the zip to your NGLLexConverter working directory. Then run NGLLexconverter.exe (there should be an icon on your desktop). Click Help in the utility dialog for more info, it's all pretty straight forward. Below is the program and a fairly recent version of the database in both TDF and Excel format zipped up together. Check out the Yahoo Groups NGL Page Files area, as this is likely where the most recent versions will be found.