In the past I have used Code Collaborator which I found was a good tool for doing code reviews. I know it integrates with SVN not sure about Eclipse directly.
I used Code Collaborator at a former employer where our version control system was Accurev. From my reading of the documentation it sound like the tool might have a better integration with SVN.
When doing Agile development sprints my teams flow for code review was we would check code into our Team Level in Accurev and someone once a day would enter all the accurev transaction ids into the Code Collaborator Gui to create a review of usually all the code that was checked in the day before. Then everyone would use the tool to leave comments ask questions etc. Generally anything that actually needed to be fixed would be reviewed in the next review.
When doing Bug fixes generally it was similar accept the Team area was more locked down so that transaction ids were from files that were kept(Accurev has an idea of saving files in like your own personal area).
Before we had this tool emailing around files and diffs was the only way code was reviewed so having a tool that allowed seeing the diffs and chatting about the particular lines of code was a lot nicer.