This online vector editor has direct access to the IAN symbols, allowing you to create conceptual diagrams in your browser for free without the need for specialized vector software. To access the symbols, click the IAN button within the diagrammer. You can save diagrams to your computer in SVG (vector) or PNG (raster) formats.
For the basics, no skills required, but some knowledge of how vector editing works will be useful for more advanced diagramming.
There is a basic video tutorial showing how to use the diagrammer on the symbol libraries resources page: http://ian.umces.edu/symbols/#_Resources
Works in all modern browsers - Internet Explorer users will need v9+, or you can install the Chrome Frame Plugin for older versions. There are currently some discrepancies between browsers and their support for SVG, with Firefox giving the best overall experience.