I run into a lot of people who do not shoot raw and do not use Lightroom, but always asked what the easiest way to add a vignette or adjust white balance. When I procede to tell them to use ACR (Adobe Camera Raw) they are suprised that they are able to. I will show you how to enable the ACR dialog box so you can take advantage of the adjustmets when working with jpgs.
Note: This method only works with CS2 and newer. First you need to dowload the latest ACR software from adobe. Once installed go to Edit > Preferences. Then select File Handling from the list to the left. Once in that menu you will see a button called Camera Raw Prefereces.
In the next dialog box you will see a drop down at the bottom JPEG and TIFF Handlingsection. From this menu select Automatically Open All supported JPEGs.
Press OK and OK again till you are out of the Preferences dialog box. That is it. Now if you go to File> Open and select a JPG the ACR dialog box should open. From there you can access all the features in Adobe Camera Raw like Vignetting, Split Toning, White Balance…ect.