Here are several useful websites for generating regular expressions:

1. regex-generator.olafneumann.org: A comprehensive tool for generating regular expressions.
2. www.javainuse.com/rexgenerator: A website that helps you create regular expressions for Java.
3. regexr.com: An online regex editor and tester with real-time matching.
4. regex101.com: A powerful regex tool that provides explanations and step-by-step analysis.
5. regextester.com: A user-friendly website for testing and generating regular expressions.
6. retool.com/utilities/regex-generator: A handy utility that allows you to generate regular expressions for different use cases.
7. regexr.com/library: A collection of pre-made regular expressions for various use cases.
8. regexlib.com: A library of regular expressions submitted by the community.
9. regexplanet.com: A website that provides a regex tester and a library of common regular expressions.
10. regexmagic.com: A tool that helps you generate regular expressions based on sample text.

These resources should assist you in generating regular expressions more effectively.