I found this list
Chromates, AgBr, As2S3, AgI, PbI2, CdS, PbCrO4(s), Hg2CO3(s), Ag3PO4(s), Bi(C6H3O3)(s), Cu(CN)2(s), Ag3AsO3(s), (NH3)3[As(Mo3O10)4](s), [SbI6]3-(aq),
Yellow seems to really like nasty metals like lead, mercury, and antimony. By far the least nasty and easiest to make of these I see is the silver ones.
Simple enough, just dissolve silver nitrate, and add the appropriate sodium salt! I bet silver phosphate will be the yellowest, I've made silver halides and they usually look black, but you should try them all!
Remember silver nitrate+light will stain skin (harmlessly).