Holga just officially released two plastic lenses that attach over the existing Holga lens to change the focal length
The two tele-converter lenses, models HT-25 (tele lens) and HW-05(wide lens) fit onto you holga and either lengthen(HT-25) or shorten (HW-05) the focal length, therefore creating a tele or wide lens.
Another new release is a fisheye viewfinder that sits on top of your holga enabling you to see the subject â€˜fisheyedâ€™ before taking the photo. This viewfinder is a companion piece to the holga fisheye lens.
More info at Holgablog