Here you can find some online tools.
With this online tool you can draw circuit diagrams. There is symbol library containing a large selection of basic component shapes, and also custom symbols can be used. The tool exports the drawn circuits as images in various formats as well as SVG-files. Also circuits can be exchanged with the generated im/export text files.
This tool belongs with the Circuit Editor to create or edit custom symbols. The created symbols are instantly availeble in the Circuit Editor when they are saved. The symbols can also be shared with other users with the im/export text files.