In the App Store right now, you will find the following apps on offer.
First up we have FX Photo Studio and FX Photo Studio HD from MacPhun. Both of these apps offer 187 effects and filters giving your iPhone photos almost endless possibilities.
FX Photo Studio is currently priced at £0.59/$0.99/€0.79 [App Store Link], whilst FX Photo Studio HD is priced at £1.19/$1.99/€1.59 [App Store Link].
Next up there is BinaryCamera, which is currently available for free [App Store Link]. This is a simple no frills black and white app from the developer of Monochromia, and is well worth a look.
Finally, iSupr8 has just been reduced to £0.59/$0.99/€0.79 [App Store Link], so if you don't already own it, and you are in to shooting video, and like that retro look, then this app is a bargain at this offer price.