First time I opened the camera app with a memory card installed, it popped a toast "Now using storage card" iirc.
You can also transfer the files manually on the phone with Astro File Manager, which is hugely popular. Move from /mnt/sdcard/DCIM/100MEDIA to /mnt/sdcard/ext_sd/DCIM/100MEDIA . You may also have pics in folders like 100PANO, etc.