How to remove wrinkles from people's faces?

a filter that can do this in one click

Maybe clean up one wrinkle in one click, but not the whole face (in one click). You can use the healing brush tool.

There are a number of plug-ins out there that are designed to improve/correct skin tone/texture etc.

Perfect Portrait, Portrait Professional, and Portraiture are three that I'm aware of; there are many more.

Depending on how you use them, results can range from natural and pleasing, to plastic/hyper airbrushed.

All are available for 30 Day Demo's, so play around with them and see which one suites your needs.

Good luck

Paul

Just to add to Paul's suggestions, if you're looking for a freebie, there's a couple set of actions called "Portrait POP" and "Photoshop Facelift" that do a fairly decent job:

http://weeklyphototips.blogspot.com/2009/01/free-photoshop-actions-at-action.html?utm_sour ce=feedburner&utm_medium=feed&utm_campaign=Feed%3A+blogspot%2FYcwX+%28Weekly+Photography+T ips%29

Thanks you so much for sharing it...

Something more useful than the dedicated portrait filters might Topaz Adjust, which has a preset that will do what you want.  It also has a host of other presets that provide some really useful affects.  I use it all the time, and you get a thirty day full function trial, and it is cheap as chips.  What you could do is download the trial period, fix your picture, and if after 30 days you no longer need it, you have lost nothing.

Wow, the healing brush worked just great!

Yes, sometimes the best solution is right under your nose (and not all these 3rd party plug-ins and filters).