RegExista is a simple web form–based application for manipulating text with regular expressions. You can use it just for testing REs, for learning/exploring REs, or incorporate it into a workflow by adding it to your Actions menu. It automatically loads text from the clipboard and copies the results back to the clipboard.
I have tried to keep it very simple. Hopefully, you can figure out how it works very quickly. If you need instructions, I've failed miserably. :) And if regular expressions scare you, it works fine for just finding and replacing normal strings.
There are only a few options: to ignore case, to replace text, and to carry over the result for multi-step operations. It also has a quick lookup drop down for some common special characters. It doesn't have all the RE flags (multiline is on) and it doesn't store REs after you've painstakingly created them. You can easily edit the drop down list in the script if you have favorites, though.
Here is a link to the application gist:
And here is a link to the required forms module (the same one used in my previous example):
P.S. Here's an example of how you could use this in a workflow, to convert tabs into spaces. Copy a script to the clipboard, open RegExista, select "Tab" from the drop down, check Replace with, and type the number of spaces you want each tab to represent (e.g. four) into the Replace with box. Press the Apply button and check the results. If it looks good, you can close RegExista and the results will be in your clipboard ready to paste back into the editor.