Question is how big/heavy, and what value? And, to what country or countries?
Normally USPS Priority or Priority Express are good options, but the limits on weight or dimensions or value can differ from country to country. Global Express is the most expensive postal option and has higher limits, but they typically ship that via Fedex these days.
The other issue is risk of chargeback; if the buyer refuses to pay importing costs like VAT or duty or delivery charge etc. some freight carriers will deliver anyway and try to charge the shipper instead of the recipient. That can't happen with USPS, but it can with UPS and Fedex. I've had Fedex try to back bill me for an open reel deck I shipped to an Asian destination, even though it was actually shipped via USPS. Of course, with me having no account in the Fedex system that effort failed completely esp. after I told them it was their responsibility to collect from the buyer, not mine. In all fairness they went away and didn't bother me after that, but it would have been much more difficult to get out of it had they been able to just charge my account.
eBay's GSP (Global Shipping Program) does a decent job of taking over those kinds of risks and making sure the seller isn't held responsible for importing costs or delivery issues. I found recently it was less expensive to get an open reel deck to Canada via that program than any other shipping option I had available, but the listing had to be structured carefully to keep the costs to a minimum.
John