Some non-hyphenated English words with consecutive double letters:
# allottee # appellee
# assessee
# balloon
# bookkeeping/bookkeeper # committee # cooee (British colloquial)
# heelless
# keenness # toolless
Bookkeeper.this is the only word i can find
Words that can be made from the letters is 'proud' are:dodourdropduoorourpodpourprodrod
Words that can be made using letters from "spring" are:GrinsPingsRingsSprigSpinPigsSignSingGinPin
Words that can be made with the letters in 'happy' are:aahhahaypapayya yap
Words that can be made with the letters in 'beets' are:bebeebesetbestbetseesettee
The longest words that I can find are the 4 letter words dopy and void. The letters also can be used to spell dip, do, ivy and pod.
I cannot find any words that use all 5 letters. The letters can be used to spell try and my.
Some words that can be made using letters from "serenade" are:EndearsSneeredEarnedErasedNearedResendSearedReseedDaresNeedsNerdsSnareEasedSandSeedSaneDareEarnEars
Some words that can be made using the letters of "environment" are:InventorOvertimeEmotiveMentionNomineeVomitEnterEventInnerMovieNerveRevertTenorTimerTonerVenomVoterTreeVetoVentNineNeonRotTinTenToe
Some words that can be found using the letters of "inventing" are:EvidentEnviedIndentIntendVentedDentDineVeinVineNineDiveEdit
Some words that can be made using the letters of "health" are:HaltHateHeathHealHeatLateAleEatAteTeaThe
Some words that can be made using the letters of "conventional" are:ConventionEvocationNonactiveNovocaineCovenantInnocentInnovateLocationVenationVocationAncientConniveContainElationToenailViolateViolentVolcanoActionActiveVioletClientInventOnlineLotion