Some of the best resources I use regularly (some perhaps slightly off-topic, but useful nonetheless):
Canva - easy graphic design tool, with many things already templated and customisable - perfect for if you want something to look professional but you’re not a graphic designer (like me!) And you can create your own document templates to use again and again - you just duplicate the document each time and customise it for whatever use etc. I use this online app almost daily!
Pixabay - free image library with all images (so long as you don’t click the ‘premium’ ones at the top) that are fine to use for commercial use.
Solopress - printers for business cards, flyers, banners, the works - really good prices, and they do free next day delivery too. I use these guys all the time. (e.g. 500 double sided matt-laminate business cards are about £20, a full size pull-up banner is around £40, A4/A3 tabletop banners around £25 etc. Really good prices)
SmallPDF - a PDF compression tool that works ridiculously well - I often have to create PDF docs that with imagery makes the file sizes huge & non-emailable - this tool compresses the file size down to mere kilobytes (I had one doc recently that was about 20Mb, and it shrank it down to 300k), without losing ANY image quality. Highly rate it.