The only thing acceptable within the rules would be to put a poster on the notice board of your flying club saying you have spare seats for a pro rata share of the overall costs as a flying buddy, or simply word of mouth. Does your club have facebook? That is also a great way to meet other like minded pilots.
Any advert for a specific flight on a specific date could easily be construed as public transport, which would require an AOC. If this was then looked into, or as previously indicated the local company with a legal AOC reported you, there would be pretty serious consequences. Certainly aerial photography is something to avoid. A lot of guys like to take pictures of nice houses, then go to the house and try to sell it to the owners. If it ever came into question who was flying when these profitable photos were taking, you could be opening a whole can of worms.
There is a "spare seats available" thread somewhere, I found a couple of flying buddies that way and saved some money when I needed to build time. If you're looking to do some trips I'm sure you'll find someone to split the cost.