The best replacement for iframe is div.

The best alternatives to iframe are rated as following:
★★★★★  div
★★★★  frame
★★★★  object
★★★★  ajax
★★★  embed
★★  frameset
★★  xfbml
★  fbml
★  object tag
★  popup
★  object embed
★  jquery load
★  embed tag
★  jsonp
★  avchd
  javascript widget
  embed youtube
  include
  php include
  master page
  portlet
  div html
  ajax div

Your alternative for iframe is not listed? Suggest!
Speaking about iframe, one probably shouldn't forget about scrollbar.

Other search terms related to iframe and their ratings are:
★★★★★ scrollbar
★★★★ scrollbars
★★★ php
★★ scrolling
★★ iframe
★★ content
★★ html
★ jquery
★ height
lightbox
onload
scroll bar
You have in mind a companion for iframe and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of iframe in all years. Click on graph for more.
iframe
div
frame