Here are some free St. Patrick's Day and shamrock symbols to download for Adobe Illustrator.
About the Symbols
Symbols are graphics you might want to use later and not have to recreate. Symbols can be used for any graphic you use frequently, like a company logo or holiday designs. Symbols are supported in Adobe Illustrator 10 and higher. These symbols are for personal use only unless written consent is acquired from the author
Using the Symbols
After saving the zip file, unzip it, and place it in your Illustrator/Presets/Symbols folder. For more information on how to use these symbols, see the Shamrock Symbols tutorial