Don and I have recently installed a wireless repeater at the Cotton Tree Caravan park Maroochydore. This is to boost the existing signal from the main Access Point at the Administration Building to the western parts of the park.
Now only a small black spot is remaining near the South West corner - we will have to gauge demand to see if installing another repeater is feasible.
The repeater is a simple Netgear WG102 Access Point configured as a WDS repeater. The antenna we used for this install is a Hills 4+4 slot (double sided) wave guide. The WG102 is a nifty little Access Point - it supports all the necessary standards and has a excellent feature set for its size and cost ($200RRP AUD). It also supports 802.3af compliant Power over Ethernet - we had to use a Linksys POE12 kit ($100RRP) with it as Netgear doesn't supply anything similar.
I housed the WG102 in a small weather proof enclosure which is screwed directly to the antenna mast.
All up it was a fairly simple exercise and didn't cost all that much - about $800 in total. Took us 3hrs to do the install. Making it all neat and using conduit etc is what takes the most time.