In most cases you have to register on the site with name, address, zipcodes, etc. It varies state to state. Feel free to amend or correct anything I missed.

ALABAMA - https://myinfo.alabamavotes.gov/voterview

ALASKA - https://myvoterinformation.alaska.gov/ (only available 7a-8p Alaska time)

ARIZONA - https://my.arizona.vote/PortalList.aspx

ARKANSAS - https://www.voterview.ar-nova.org/voterview

CALIFORNNIA - https://california.ballottrax.net/voter/

COLORADO - https://www.sos.state.co.us/voter/pages/pub/olvr/findVoterReg.xhtml

CONNECTICUT - https://portaldir.ct.gov/sots/LookUp.aspx

DELAWARE - https://ivote.de.gov/VoterView

DISTRICT OF COLUMBIA - https://www.dcboe.org/Voters/Absentee-Voting/Track-Absentee-Ballot

FLORIDA - https://www.dos.myflorida.com/elections/for-voters/check-your-voter-status-and-polling-place/ballot-information-and-status-lookup/

GEORGIA - https://www.mvp.sos.ga.gov/MVP/mvp.do

HAWAII - https://ballotstatus.hawaii.gov/

IDAHO - https://idahovotes.gov/online-voter-tools/

ILLINOIS - https://ova.elections.il.gov/RegistrationLookup.aspx (individual counties may have better info?)

INDIANA - https://indianavoters.in.gov/

IOWA - https://sos.iowa.gov/elections/absenteeballotstatus/absentee/search

KANSAS - https://myvoteinfo.voteks.org/VoterView

KENTUCKY - https://vrsws.sos.ky.gov/VIC/

LOUISIANA - https://voterportal.sos.la.gov/

MAINE - https://apps.web.maine.gov/cgi-bin/online/AbsenteeBallot/index.pl

MARYLAND - https://voterservices.elections.maryland.gov/votersearch

MASSACHUSETTS - https://www.sec.state.ma.us/wheredoivotema/track/trackmyballot.aspx

MICHIGAN - https://mvic.sos.state.mi.us/Voter/Index

MINNESOTA - https://mnvotes.sos.state.mn.us/AbsenteeBallotStatus.aspx

MISSISSIPPI - https://www.sos.ms.gov/Elections-Voting/Pages/County-Election-Info.aspx (MUST TRACK BY COUNTY - NOTHING STATEWIDE)

MISSOURI - https://www.sos.mo.gov/elections/goVoteMissouri/localelectionauthority (MUST TRACK BY COUNTY - NOTHING STATEWIDE)

MONTANA - https://app.mt.gov/voterinfo/

NEBRASKA - https://www.votercheck.necvr.ne.gov/voterview

NEVADA - https://nevada.ballottrax.net/voter/

NEW HAMPSHIRE - https://app.sos.nh.gov/Public/AbsenteeBallot.aspx

NEW JERSEY - https://www.nj.gov/state/elections/vote-track-my-ballot.shtml

NEW MEXICO - https://voterportal.servis.sos.state.nm.us/wheretovote.aspx

NEW YORK - https://nycabsentee.com/tracking

NORTH CAROLINA - https://vt.ncsbe.gov/RegLkup/

NORTH DAKOTA - https://vip.sos.nd.gov/AbsenteeTracker.aspx

OHIO - https://www.sos.state.oh.us/elections/voters/toolkit/ballot-tracking/

OKLAHOMA - https://okvoterportal.okelections.us/

OREGON - https://secure.sos.state.or.us/orestar/vr/showVoterSearch.do?lang=eng

PENNSYLVANIA - https://www.pavoterservices.pa.gov/Pages/BallotTracking.aspx

RHODE ISLAND - https://vote.sos.ri.gov/Home/UpdateVoterRecord?ActiveFlag=3

SOUTH CAROLINA - https://info.scvotes.sc.gov/eng/voterinquiry/VoterInformationRequest.aspx?PageMode=AbsenteeInfo

SOUTH DAKOTA - https://vip.sdsos.gov/VIPLogin.aspx

TENNESSEE - https://tnmap.tn.gov/voterlookup/

TEXAS - https://www.sos.state.tx.us/elections/voter/cclerks.shtml (MUST TRACK BY COUNTY - NOTHING STATEWIDE)

UTAH - https://votesearch.utah.gov/voter-search/search/search-by-voter/track-mail-ballot

VERMONT - https://mvp.vermont.gov/

VIRGINIA - https://www.elections.virginia.gov/citizen-portal/

WASHINGTON - https://voter.votewa.gov/WhereToVote.aspx#/login

WEST VIRGINIA - https://services.sos.wv.gov/Elections/Voter/AbsenteeBallotTracking

WISCONSIN - https://myvote.wi.gov/en-us/myvoterinfo

WYOMING - https://sos.wyo.gov/Elections/Docs/WYCountyClerks.pdf (MUST TRACK BY COUNTY - NOTHING STATEWIDE)