hey granpa, welcome to fsb.
useful suppliers depends on where you are. a rough location would help narrow it down.
speaking for the uk, the two i use most are dr tweek and bitsbox. they are pretty much geared up to stompbox building so source a good range of stomp-appropriate parts of audio-grade quality. they also know the difference between a useful germanium diode and an olive on a cocktail stick, which is not the case with a few ebay sellers. but obviously, the prices reflect that attention to detail.http://doctortweek.co.uk/
(shop temporarily being rebuilt)http://www.bitsbox.co.uk/
for more involved dedicated bits like specific pcbs, belton brick, etc, i use fuzzdog pedalparts.http://shop.pedalparts.co.uk/
have had excellent service from all the above.
there are a few other uk places but they seem (to me) to be for bulk orders, if you are making lots of pedals, rather than one-offs.
for resistors (the bits you will use most of) it's probably worth buying a kit of various values (10 or 20 of each) to get you started. a lot cheaper and less fiddly than ordering odd bits as you go along. something like this is a good beginners kit (well i got it and i thought so) http://www.ebay.co.uk/itm/161270963805
also worth using chinese ebay sellers for bulk ordering offboard things (10x 100K pots, 10x jacksockets, etc) you will always need. but maybe hold back with that until you really get the habit and know you will definitely use them all.
enjoy your building,