as indicated... But after the most recent iMovie upgrade, I would be pretty careful with that... iMovie HD (AKA: iMovie 5, I think) was the first version to handle high definition. iMovie 6 got along well with those files. The most recent version of iMovie (included with iLife 08) is not backward compatible with iMovie 6 - and folks who upgraded yelled loud enough at Apple that Apple is now allowing iMovie 6 to be a free download.
An hour of standard def video takes ~ 13 gig of hard drive space on your computer and an hour of hidef video takes 3x-4x more space.
Then, depending on how you work your iMovie projects, no matter what you do, you can get back to the original clip - not quite "non-destructive" editing as in FinalCut, but the end result is that the iMovie files end up keeping a LOT of information (hence taking up unnecessary hard drive space).
The Share... activity should be to save the file as "Full Quality" Quicktime. These are pretty big files, too... but it should accomplish what you want to do (and get rid of all the unecessary file iMovie was saving for you). Depending on the length of these projects will determine whether a DVD will hold what is needed or if large external hard drives are required.
The other issue is whether the poster's video editing application has these "save as" capabilities... I have no clue.
By the way, I just did one so I checked the file sizes... The original capture camcorder was my Sony HDR-HC1 onto miniDV tape as HDV (1080i)... then imported over FireWire to iMovie...
I started with about three hours of footage (over 100 gig). After all the editing was done, I moved remaining unused clips in the Clips pane to the trash and emptied the trash... The resulting iMovie project file size is now ~53 gig and the edited video in the timeline is 3 minutes: 40 seconds: 21 frames. Just to make it easy, I did a "Share: Full Quality". The resulting file is 2.22 gig... When I am ready, I can re-import this HD (.mov) video file to iMovie or FinalCut and move it out to HD-DVD or BluRay. I chose to export the project back to my camcorder because miniDV tape is cheap - and it is easy to do.