Time Warp

I see you used the polar/rectangular filter. If you resize the picture to a square, then use polar/rectangular, then rotate 180 degrees or flip vertical, then rectangular/polar again, then you will get a perfect circle that you can cut and paste into another image. Or after you copied it and undid all the steps to before where you used the p/r you could paste it as a separate layer on top of your original image and apply other effects to the circle layer.

Examples here: www.deviantart.com/eternatease…
www.deviantart.com/eternatease…
www.deviantart.com/eternatease…
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www.deviantart.com/eternatease…
www.deviantart.com/eternatease…
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www.deviantart.com/eternatease…
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www.deviantart.com/eternatease…
www.deviantart.com/eternatease…

Oh yeah, and look at the free Mehdi plugins, Johann's filters, and Xero free plugins ☺