With the Macs connected to the same network, launch iPhoto on each Mac, choose iPhoto > Preferences and click the Sharing tab. Enable the Look For Shared Photos and Share My Photos options on each Mac. Under the Shared entry in iPhoto’s Library pane, you should see the name of your other Mac.
Now select your other Mac, navigate to the pictures you want to copy to your Mac, and select them. Drag them to iPhoto’s Photos entry on your Mac. They’ll be added to that Mac’s iPhoto library. Alternatively, you can drag them into an album on that Mac, and they’ll be added to the album.
You can also import entire albums from one Mac to another. Just select the album you want to import from the remote Mac and drag it to the Photos entry on the Mac you’re sitting in front of. It will import as an untitled event. Control (right) click on one of the images, choose Show Event and you’ll be taken to the event that contains these images. You can now click on the Untitled Event entry at the top of the window and rename the event to something that’s easier for you to find.
Given how easy it is to grab images from another Mac using this technique, it’s in your best interest to switch on the Require Password option in iPhoto’s Sharing preferences, particularly when you’re out and about using public Wi-Fi.