There are many fun lo-fi cameras out there, and trying to figure out which one to get can be confusing. If you are new to film photography, you should consider starting with a lo-fi 35mm film camera. Why?
1. Lower cost of film. You get more frames per roll, and if you are a beginner, the way to get good at shooting with film, is to shoot lots of it. I find that when beginners use 120 film, it's higher costs and higher cost of processing keeps them from shooting because they are very much aware of how much each shot costs.
2. Easier to find. 35mm film is much easier to find than the 120 film used in the Holga 120 cameras. I see it in the drugstores, as well as few grocery stores (although that is becoming a much rarer experience).
3. Easier to get processed. Most drugstores and large big box stores like Target or Walmart still have 1-hour labs, but only for 35mm film. You will have to find a local lab to process your 120 film, or send it out.
4. Lower cost of processing. It cheaper to get your 35mm film processed. If you skip the prints and just get the roll processed and put on CD, you can cut the cost down even more. Tip: If you want prints, then you only pay for the ones that came out. This keeps the cost of processing down.
Take a look at one of these 35mm cameras:
Holga 135 or 135BC
Similar cheap lens and operation as the Holga 120 cameras. 1 aperture setting (yes, the camera has 2 settings, but they are identical), 2 shutter settings, N (1/100 sec) and B (Bulb setting) tripod mount, cable release socket If you want the corner vignetting like on the larger format camera, get the Holga 135BC.
Sample photos: http://www.flickr.com/groups/holga135bc/
Superheadz Black Slim Devil
This is a clone based on the popular vintage Vivitar Ultra Wide and Slim. It has no exposure controls and no flash option, but with it's wider than normal lens (22mm) it is capable of taking some outstanding photos.
Sample photos: http://bit.ly/kSlimCamSample
There is a bigger pool of sample photos from the Vivitar UWS, which the Slim camera is based on:
The Lomography La Sardina
This is a newly designed camera by Lomography, that has many nice features. It has a super wide angle lens, similar to the Superheadz Slim cameras, but has many extra features. It has a powerful dedicated flash unit made especially for it, as well as a "B" shutter setting, tripod mount, and a double exposure switch.
Sample photos: http://www.flickr.com/groups/1692440@N20/
The Lomography Diana Mini
Lomography took the Diana camera, and shrunk it down to 35mm format. The Mini, while it lacks the interchangeable lenses of the full sized Lomography Diana+, is still a feature packed camera (at least compared to the Holga and Black Slim Devil). The frame format is unusual. They stuck with the square format of the Diana camera, but it is centered on a standard 35mm frame. The reason for floating the square on the 35mm frame is that be using a standard 35mm format, most 1-hour labs will be able to more easily deal with making scans or prints, since they are set up for regular 35mm film. You can also set the camera to half-frame 35mm, which is 2 vertical 24mm x 17mm images. This translates to 2 images on a standard 35mm frame. Currently a favorite of mine, it lives in my camera bag so it is handy where ever I go. 2 aperture settings, 2 shutter settings, N (1/100 sec) and B (Bulb setting) tripod mount, cable release socket This camera is unusual in that it offers square format,24x24mm on a standard 35mm frame (24x36mm). It also offers a half frame option, 17x24mm frames (it doubles the number of exposures you get on a roll of film)
Diana Mini sample photos: http://www.flickr.com/groups/1232275@N22/
The Diana Mini is nice, but I find that unless I am working close and with a flash, the images tend to be on the softer focus side, to the point of being blurry. You might want to consider the sharper lens of the Superheadz Slim cameras (Black Slim Devil, White Slim Angel or other variant, all the same camera in diff colors). Take a careful look at the sample photos on Flickr to help you make a decision.
I have Out of the Box Videos posted on my youtube channel:
Superheadz Black Slim Devil: http://bit.ly/superheadz_slimcam
La Sardina: http://bit.ly/kSardinaBox
Holga 135BC: http://bit.ly/kHolga135Box
Diana Mini: http://bit.ly/kMiniBox
Whichever camera you choose, remember that the point of lo-fi photography is to have fun and don't sweat the details!