Question: For example, I want to play all 58 videos uploaded by a single user.

Obviously I could create a playlist, add each video to it, then play the entire playlist, but is there a simpler way?

Answer: 
Little trick I found is to get a user's unique code/string from their profile page's source. Here's how to do it:

* Go to their user page and right-click -> "view page source".
* Search for "vnd" and copy the code that you find (It should start with "UC").
* Open one of the user's videos. In the URL address, add the following to the end: "&list=" then paste the string you copied.
* Final step is simply change the 2nd character of the code you pasted from a C to a U. Hit enter and the video should reload, and now it appears in a playlist of all the user's videos.

This seems to work pretty reliably, but sometimes does not get all of the user's videos.
Here's a bookmarklet & code for uploads playlist. Copy and save the line below as a bookmark, open a YouTube video and click the bookmark to load the user's uploads playlist. I don't think a public or auto-generated playlist of all uploads exists, only recent uploads, which is the same as what you see when you click play in the corner of a user's playlist called uploads, and the same you'll find by using this bookmarklet

**Bookmark:**

```
javascript:(function()%7Bif%20(window.location.href.indexOf(%22watch%3Fv%3D%22)%20%3E%20-1%20%26%26%20window.location.href.indexOf(%22%26list%3D%22)%20%3C%200)%20%7Bwindow.location%20%2B%3D%20%22%26list%3D%22%20%2B%20%22UU%22%20%2B%20document.documentElement.innerHTML.match('channelId%22%20content%3D%22(.*%3F)%22')%5B1%5D.substr(2)%3B%7D%7D)()

```

**Javascript:**

```
if (window.location.href.indexOf("watch?v=") > -1 && window.location.href.indexOf("&list=") < 0) {
  window.location += "&list=" + "UU" + document.documentElement.innerHTML.match('channelId" content="(.*?)"')[1].substr(2);
}

```

Note, as mentioned on this page, simply appending "&list=UL" to the video URL doesn't work as desired.

Also worth mentioning this only really works if you load the channel's latest video then use the bookmark

Credit for the bookmarklet method goes to REast and [his comment below](https://webapps.stackexchange.com/questions/9702/#61391).