I'm actually working on something now. I have it set up for me only because i use it to keep track of my inventory across multiple accounts. It is a windows based program with a website to display items for people to see.
My biggest concern i had was people entering information and then not updating it making there items outdated. However, I think i know of a solution. If I make items expire after a week but give an option for the user to re-list items without typing any info, the list of items will always be updated.
The reason why i would love to release this program to the public it is would make finding stuff a little easier than hopping around to different guild stations.
Will people use it ? I don't know. I just know i like it.