I started writing a full account of my resupply stops along the trail, with comments about the selection and variety different places had. The list grew longer, and I think that most of this information can be found on Yogi’s excellent book. It was also not very interesting.
Instead, I’ll just post about the different locations I mailed myself packages, which will make it all shorter and to the point.
For residents of the US (= the majority of hikers), a friend/family member who can ship packages along the trail might be an option. I preferred to rely just on myself along the trail. In general, I tried avoiding sending myself packages whenever I could. Most trail towns had decent resupply options, and I only sent packages when (I thought) I had to.
So, here is a list of places I bought food in bulk, and mailed it to myself further up the trail:
In San Diego I bought some food, and sent it ahead to [Warner Springs] (mile 109.5) and [Ziggy and The Bear] (mile 210.8). In retrospect, I think there is no need for a package in Warner Springs - the community center had a reasonable selection over there, with the prices being a bit higher than normal stores. I would have definitely managed to buy what I needed, If I didn’t have a package waiting for me there.
At Ziggy and The Bear it might be a bit harder to bu food, though it is possible to get some basic stuff from them (if available), or try to hitch out to a supermarket if all else fails. Still, a package there was very helpful.
Agua Dulce (mile 454.5)
At Agua Dulce’s Hiker Heaven (which seems to be closed next year. UPDATE: re-opened for 2016), I joined the shuttle heading out to REI and WalMart, and bought supplies for the Sierras. I sent out a package to Kennedy Meadows (mile 702.2), Vermillion Valley Resort (mile 878.8) and Toulumne Meadows (mile 942.5).
The package at Kennedy Meadows was helpful (though it costs $5 to get it from the store, if I remember correctly), but the store does have plenty of hiker supply selection. The price is high over there, but I believe it is possible to rely on it, and skip the package.
The VVR package is similar. The store does have some selection, though it seemed like it has fewer items, and the prices are steeper even in comparison to KM. The price of getting a package there was $20, so maybe with the cost of sending it (~$17) it would be more cost-efficient to just buy stuff there. Having the next stop (Mammoth Lakes) only 1.5 days later, makes it easier to make do with whatever they have in the store.
The Toulumne Meadows package was not there when we got to the store, and was waiting for us down in Yosemite Valley. Luckily, we were going to the valley anyway. The general store had plenty of resupply options, and so did the stores down in Curry Village and the Housekeeping Village. So there’s no special need to send a package over there anyway. To conclude - All 3 packages from Agua Dulce can be skipped, if you don’t mind paying a bit extra for your resupply, and maybe have a smaller selection to choose from.
South Lake Tahoe (mile 1092.94)
The small store in Sierra City might be enough for resupply, but the selection is not too impressive. Same goes for the store in Old Station. Both places might work out for you, but having the packages was a bit easier for us.
Ashland (mile 1727)
In Mazama Village, the store has some options, but I was happy I had my package, since there weren’t that many vegetarian meals around. Same goes for Shelter Cove (I had a toaster oven pizza there for dinner). Timberline Lodge didn’t have any resupply store around it (Though the AYCE buffet was filling and tasty). So all in all, I was happy I had those packages.
Cascade Locks (mile 2155)
At my final major stop, I got a (very helpful) ride with Rock Ocean, and bought my Washington supplies at the Walmart and Safeway in Hood River. The Walmart sucked, by the way. Safeway was much much better.
I made packages to Trout Lake (mile 2237.5), White Pass (mile 2303), Snoqualamie Pass (mile 2402), The Dinsmores (mile 2476), and Stehekin (mile 2580.2). A lot of packages, for a lot of money (~$17 * 5 + 1 bounce box).
The small store in Trout Lake might have been enough for me, and I haven’t really checked the offerings at the gas station in Snoqualamie Pass, but having those packages did make everything simpler.
I used a bounce box along the trail, mostly to ship ahead items I might need further down the trail, and map pages I didn’t want to carry with me. I sent it ahead many times, until I finally gave it up in Ashland. I did send a smaller box from there to Bend, and then to Cascade Locks, and to Seattle. Almost everywhere I had the box shipped to, I opened it, and then payed to have it shipped ahead, so it wasn’t very cost-effective (I think I bumped it for free only once, in Wrightwood).
For the box itself, I used a 5 gallon plastic bucket I bought at the Walmart in San Diego.
This is a quick rundown of all the places I had the box shipped to, in case anybody wonders:
San Diego → Idyllwild → Big Bear City → Hiker Heaven → Kennedy Meadows → Lone Pine → Mammoth Lakes → South Lake Tahoe → Quincy → Mt. Shasta City → Ashland → Bend → Cascade Locks → Seattle