For shipping, if your package is under 13 ounces, you can use stamps and drop it in the mailbox. It doesn't matter if it is 1st class or priority. You might be able to save some $ by shipping 1st class. you can get 50 bubble mailers for around 20 cents/ea on ebay.
I've been curious about this - I'm preparing to release a kit that will tentatively be in the under $30 category, and $5.20 for the smallest flat rate priority mail box seems like a large percentage of the kit value.
Have folks had experience shipping small kits in padded mailers by first class mail?
The only components I'd be particularly worried about crush damage to are an 8-pin DIP IC and perhaps its socket - perhaps if I found some old plastic IC tubes to cut up. There's also a very flat 36mm speaker, but some of these come in their own tiny bubble envelopes, or I could tape them into a fold of cardstock.