Common words:
* abolish
* abruptly
* absence
* absorb
* account
* accurate
* address
* adverse
* advised
* affects
* agency
* agility
* agreed
* aisle
* alarm
* alcohol
* almonds
* already
* although
* amnesia
* analyse
* ancient
* animals
* announce
* another
* answers
* anxiety
* anywhere
* appoint
* archive
* around
* arrange
* arrest
* arrive
* artists
* asleep
* assist
* assume
* athletic
* attack
* attempt
* attend
* attract
* audible
* author
* autumn
* avenue
* awaken
* awards
Less common words:
* abashed
* abdicate
* abolish
* aborted
* abridge
* abrogate
* abscond
* absolve
* accede
* accent
* accept
* access
* acclaim
* accuse
* achieve
* acidify
* acquire
* acquit
* across
* acted
* active
* actor
* acutely
* adapt
* addict
* addled
* adjourn
* adjudge
* adjust
* admire
* admit
* adopt
* adore
* adrift
* advance
* adverse
* advice
* advise
* aerial
* affair
* affect
* afford
* afraid
* aghast
* agitate
* ailment
* aimless
* airless
* alight
* allied
* allow
* allure
* almond
* almost
* alpine
* already
* altar
* alter
* amaze
* ambush
* amend
* amends
* amidst
* amused
* anchor
* ancient
* angle
* angry
* animal
* annoy
* annual
* answer
* anthem
* anticip
* anxiety
* anxious
* apart
* apathy
* appeal
* appear
* append
* appetite
* apply
* appoint
* approve
* arched
* archive
* ardent
* arouse
* arrant
* arrive
* arrow
* artery
* ascend
* ascribe
* ashamed
* aside
* askance
* asleep
* aspect
* aspire
* assail
* assault
* assemble
* assert
* assess
* assign
* assist
* assume
* assure
* astonish
* astound
* attach
* attack
* attend
* attract
* auburn
* audible
* auditor
* augment
* austerity
* author
* avail
* avenue
* average
* avert
* awaken
* awkward
This is not an exhaustive list, but it provides a good starting point for finding eight-letter words that begin with "a."