When you import videos to iPhoto from, say, an iPhone, the videos get dumped in with all the snapshots you've taken. Thankfully, there is an easy way to separate out the videos by using a Smart Album.
A Smart Album is an album iPhoto creates for you, based on criteria you specify. You can use iPhoto's Faces or Places features, for example, to create Smart Albums containing certain people or images shot in certain locations. When you import new photos that meet that criteria, the photos are added to the appropriate Smart Album. And in my experience of creating a Smart Album for to collect all of my videos, it appears iPhoto scanned the existing library and added previously imported videos to the smart album.
To create a Smart Album, choose File > New > Smart Album. A window will pop up, where you can name the album and create conditions for its contents. For a Smart Album of videos, simply choose "Photo" from the left pull-down menu, choose "is" from the center pull-down, and "Movie" from the right pull-down. Clicking on the plus sign to the right of the conditions will let you add another condition. Don't like the new condition? Then hit the minus sign to delete it.
After you create a Smart Album, connect your iPhone or another video device and import the contents into iPhoto. The videos should appear in the smart album, along with any older videos that you might have had in your library.
To edit the Smart Album, right-click (or, to be specific, click while holding two fingers on the trackpad) on the title of the album in the left-hand column and select Edit Smart Album.
Click here for another Smart Album tip that separates the shots you take with your iPhone 4's front-facing and rear-facing cameras. Have a Smart Album that you find incredibly useful? Let us know in the comments below.