Check in for your flights here.  Be sure to have your confirmation number and the name of the passengers.

Air Canada Check-In and Baggage Information:

http://www.aircanada.com/en/travelinfo/traveller/checkin/

http://www.aircanada.com/en/travelinfo/airport/baggage/index.html

Air Jamaica Airlines Check-In and Baggage Information:

http://www.airjamaica.com/WebCheckIn.aspx

http://www.airjamaica.com/Manage_Baggage.aspx 

AirTran Airways Check-In and Baggage Information:

https://ebyepass.airtran.com/CheckIn.aspx

http://www.airtran.com/policies/carry-on_checked.aspx

Alaska Airlines Check-In and Baggage Information:

https://webselfservice.alaskaair.com/checkinweb/default.aspx?language

 http://www.alaskaair.com/content/travel-info/policies/baggage-checked.aspx

American Airlines Check-In and Baggage Information:

https://www.aa.com/reservation/findReservationAccess.do

https://www.aa.com/i18n/travelInformation/baggage/main.jsp?anchorEvent=false&from=Nav

British Airways Check-In and Baggage Information:

http://www.britishairways.com/travel/olcilandingpageauthreq/public/en_gb

 http://www.britishairways.com/travel/bagchk/public/en_gb

Continental Airlines Check-In and Baggage Information:

http://www.continental.com/travel/checkin/start.aspx

http://www.continental.com/web/en-US/content/travel/baggage/default.aspx

Delta Airlines Check-In and Baggage Information:

http://www.delta.com/traveling_checkin/index.jsp

http://www.delta.com/traveling_checkin/baggage/

Frontier Airlines Check-In and Baggage Information:

http://www.frontierairlines.com/plan-book/online-check-in

http://www.frontierairlines.com/faqs/baggage-faqs

Hawaiian Airlines Check-In and Baggage Information:

https://apps.hawaiianair.com/checkin/

http://help.hawaiianair.com/app/answers/detail/a_id/80/~/carry-on-bags-%2F-check-in-luggage

Jet Blue: Check-In and Baggage Information:

http://help.jetblue.com/SRVS/CGI-BIN/webisapi.dll?New,Kb=askBlue,case=obj(4315)

 http://help.jetblue.com/SRVS/CGI-BIN/webisapi.dll?New,Kb=askBlue,case=obj(634)

Lufthansa Airlines Check-In and Baggage Information:

http://www.lufthansa.com/us/en/Online-Check-in-Info

http://www.lufthansa.com/de/en/Baggage-guide 

Southwest Airlines Check-In and Baggage Information:

http://www.southwest.com/flight/retrieveCheckinDoc.html

http://www.southwest.com/html/cs/landing/bags_flyfree.html

Spirit Airlines Check-In and Baggage Information:

https://www.spirit.com/Default.aspx#check-in

http://www.spirit.com/OptionalFees.aspx

United Airlines Check-In and Baggage Information:

http://www.united.com/page/article/0,6867,50446,00.html?jumpLink=%2Fcheckin

 http://www.united.com/page/middlepage/0,6823,1031,00.html

US Airways Check-In and Baggage Information:

http://www.usairways.com/en-US/FAQs/webcheckin.html

http://www.usairways.com/en-US/traveltools/baggage/default.html

Virgin America Airways Check-In and Baggage Information:

http://www.virginamerica.com/online-check-in.html

http://virginamerica.custhelp.com/app/answers/list/p/75/search/1

Virgin Atlantic Airways Check-In and Baggage Information:

https://www.virgin-atlantic.com/en/us/manageyourflights/diycheckin/index.jsp

http://www.virgin-atlantic.com/gb/en/travel-information/baggage.html