Transportation:
http://www.baltimorewatertaxi.com/
http://www.charmcitycirculator.com/
Historical:
http://www.nps.gov/balt/planyourvisit/guided-walking-tours.htm
http://baltimore.org/listings/attractions/baltimore-national-heritage-area-trails-tours
http://baltimore.org/see-do/historical-attractions
http://www.historicbaltimore.org/program/bulletinboard.htm
http://www.baltimore-maryland.org/history/baltimore-history.html
The National Aquarium in Baltimore:
http://www.aqua.org/
The Planetarium at the Maryland Science Center:
http://www.mdsci.org/planetarium/
The IMAX at the Maryland Science Center:
http://www.mdsci.org/imax/
Miscellaneous Links:
http://baltimore.org/see-do/inner-harbor-attractions
http://www.harborplace.com/
http://www.thegalleryatharborplace.com/en.html
http://www.southbaltimore.com/innerharbor/harborplace/