It depends what kind of labelling you want - temporary or permanent.
I got some embroidered labels made that I put on quilts. The labels are small; they say "Made by Jennifer" which is both personal enough for me, and also anonymous enough for me. I think I got 50 for $20ish. I got them from the Dutch Label Shop, but there are plenty of other places that will make them. If you want a logo the cost goes up, but they're still pretty reasonable for large items.
For smaller items that will still be washed, I make little hang tags out of card stock that include washing instructions. You can get a craft punch that punches out little tag shapes, but I just cut them into rectangles with an old rotary cutter and ruler. I hole punch the corner, attach a loop of ribbon, and pin the ribbon to the item (the tags get ripped too easily if you pin them directly to the item). You could print a logo on tags like these if you wanted them to be identifiable in a shop.
For really small things (like greeting cards or silly pencils) I just use little price stickers from the dollar store.
Good luck with thinning your stash!