I have been asked by a client to put together end-user documentation for several software applications. I am trying to find resources that will help me in estimating the time required to create these documents. Any personal experience or sites that I could go to? Thanks!

Have you contacted the Society for Technical Communication?

As a side note - consider carefully what they're asking for. Be sure to include time for careful analysis in your proposal.

It really depend what you want. If you are creating use manuals, then it depends on the level of detail, required screenshots and so on. If you want to just get a rough idea, estimate the number of pages for all documents and they estimate the time required to complete them. There is no right or wrong answer here. A lot of it comes from experience in a specific domain.

Hope this helps.

I think you'll get the help you want at the tech writers' mailing list TECHWR-L Go to Community and subscribe to the list. Good stuff.

How familiar are you with the software that you will be writing about?