I was asked by people of image hosting that they can use without registration. So here is the list:

www.gizzabit.com
http://bayimg.com
http://paintedover.com/
http://sighost.techstarcomputers.net/
http://www.digitaluploader.com/
http://www.imagehigh.com/
http://www.imagepilot.com/
http://www.imagevenue.com/
http://www.imgspot.com/
http://www.pixfiles.net/index.en
http://www.pixilive.com/
http://www.pixpond.com/
http://www.savefile.com/upload.php
http://www.uploadimages.net/index.php
http://www.uploadyourimages.com/

And here is the list of image hosting provider that require registration

http://free-image-hosting.org/
http://www.putfile.com/
http://www.uploadit.org/
http://geocities.yahoo.com/
http://imageevent.com/
http://onfinite.three10.com/
http://picserver.student.utwente.nl/
http://photobucket.com/
http://walagata.com/
http://we-todd-did-racing.com/
http://www.applepics.com/
http://www.blamethepixel.com/sigupload.php
http://www.bravenet.com/
http://www.datazap.net/
http://www.filehigh.com/
http://www.freepichosting.com/
http://www.hpphoto.com
http://www.hunt101.com/
http://www.imagehost.com
http://www.imagemagician.com/
http://www.imagestation.com/
http://www.listtailor.com/
http://www.miamihost.net/
http://www.mypicgallery.com/
http://www.pbase.com/
http://www.photoaccess.com/
http://www.photoasa.com/
http://www.photobucket.com/ *
http://www.photodump.com/
http://www.photogra.com/
http://www.picturetrail.com
http://www.realimagehost.com/
http://www.rollingedits.com/
http://www.sighost.com/
http://www.spymac.com/
http://www.streetneeds.com/
http://www.strike9.com/
http://www.villagephotos.com/
http://www.yoxio.com/member.php

UPDATE:

List of image hosting dont require registration

http://alkaspace.com/
http://ephotohut.com/
http://fileave.com/
http://host-a.net/
http://photobucket.com/
http://photobucket.com/
http://www.filehigh.com/
http://www.filenanny.com/
http://www.freeimagehome.com/
http://www.freefilehosting.org/
http://www.freemyimage.com/
http://www.gigafiles.co.uk/
http://www.hotlinkfiles.com/
http://www.img4free.com/
http://www.image-upload.net/
http://www.myfilestash.com/
http://www.mynetimages.com/
http://www.photopeg.com
http://www.photojerk.com/index.php
http://www.photoserver.us/
http://www.picturerack.com/
http://www.postthatpic.com/
http://www.snapdrive.net/
http://www.theimagehosting.com/
http://www.thepixplace.com/
http://www.villagephotos.com/
http://www.yesalbum.com/