I use Pirateship to ship games being sold/traded. USPS Ground is a boon if you have a box. USPS Priority Mail is cheaper than getting the label direct from USPS. More on reddit.com

If it doesn’t say flat rate, then it’s usually calculated by size and weight. Go to the post office and they’ll help you get whatever you need. More on reddit.com

Depends on weight, most of the flat rate boxes are cheaper for anything over a couple pounds. More on reddit.com

I used Lugless recently to ship 6 large heavy duty Home Depot moving boxes (each ~65 lbs), and it went pretty well! They go through UPS or FedEx depending on your location and are much cheaper than shipping directly through UPS/FedEx. I dropped them off at a UPS in Providence on Tuesday morning, and they arrived in Miami on Friday. I ended up getting the Essential insurance plan (which guarantees a delivery date and insures up to $500 per box) for about $60 I think, so total was around $390 after tax. You can choose to go with no insurance too, but they do have 3-4 options at different price points. My boxes were mostly full of clothes and books, so they were relatively heavy. Smaller and lighter boxes will cost less. Based on my box dimensions and weight, it was about $48 per box (not including insurance). I also shipped to a residential address, which added another $20-30 charge to the total. I believe there’s no extra fee if you ship to a UPS/FedEx store. Definitely use lots of tape and bubble wrap - the boxes will probably be tossed around a bit if you’re shipping them far. I taped top, bottom, and all corners on these 6, and I wish I had taped the edges too. None of my boxes arrived with holes or anything, but they did look a little bit squished down (i.e., they probably had a bajillion other boxes stacked on top of them). More on reddit.com