There are a few tools I worked on, but I'm not sure how useful they are or if anyone would be interested.
This one lets you split your 3D model along some planes, so it can fit in your 3D printer:

This one tells you if the part will fit in your 3D printer:

This one will help you add some holes in your 3D model:

This one can help you make 3D eyes from a vertex group:

So far those tools are kinda tailored to my needs and need more work, I'm very much open to requests though