I have a customer who wanted help with getting a landing page onto their wi-fi. Now Coova networks has some solutions and pay-per-month services exist where users can log in exchange for making an account do exist. A link and name is needed but there is also Wifi Dog which is an open source project that does something like this as well.
I found this goldmine article from flashrouters.com for the latest dd-wrt compatible router recommendations and they seem like they have great customer service. I am trying to find an excuse to buy from them just for that reason. For a simple splash page, I have found that many people recommended a plug in for dd-wrt called NoCatSplash – but if the router where NoCatSplash is installed is not controling the DHCP (Windows recommended best practices) then that feature is disabled. Well, that was my intent – however one could install it as a router within the LAN network. Lets keep looking around. Worldspot.net has a solution that is used with Coova enabled routers for a splash page as well.