I just bought a new KHS Brentwood in anticipation of commuting to work. When I bought the bike, I also bought a few accessories including two spare tubes. When I got home, I noticed the tubes are size 700/32 but the bike has tires that are 700/38. Will these tubes work? Am I better off getting tubes that fit my 700/38s better or will these 700/32s be fine? Thanks.

The 32's will work fine. Because they're (slightly) small for your tires, they'll be stretched a little thin--you might be slightly more prone to flats. But only slightly. They are certainly fine for spares.

I agree with UWengineer. Some weight-weenies I know use smaller tubes to shave a few micro-grams. They will work fine.

Or we buy the wrong size then appear to be weight weenies. I was running some 19-26 m tubes in some 32 C tires. They mostly worked. Felt squishy at low pressures along the sidewalls, like you could feel the tire, then the tube...