Login into multiple framed or unframed outside pages using single login entry splash page

Login into multiple framed or unframed outside pages using single login
entry splash page

Have a page that has 3 vendor related login pages iframed in. Clients
often times are given the same login information for all three of these
outside pages, but have to login three times to use them. Is there an easy
way or best practice to set up a login splash form that feeds the login
information into these frames, or into new loaded portals to the vendor
pages so they don't have to do the end user doesn't have to do the work
three times.
Main page is http://www.fhkaysing.com/ These are presently being iframed
in: under menu titles
WebLink Login Carrier Upload E-Tracker
http://www2.fhkaysing.com/WebLink8/ &
http://www2.fhkaysing.com:9300/fhkfiletracker/UploadLogin.aspx &
http://www2.fhkaysing.com:9300/fhkfiletracker/FHKEtrackLogin.aspx