Okay, this tutorial will feature Will Young as that's all I can be asked to find. Anyhoo on with the tutorial
Open Photoshop and make a new image 750px wide by 325px high. Make sure the background is white
Arrange your pics on your canvas so that each one overlaps the next one
Make sure the first layer is selected, then click the layer mask tool
Then select the gradient tool and go to the gradient editor and make sure the foreground to background is selected, click ok and then press D to reset the colours to their default black and white
Next comes the fun bit, go to your first pic and drag the cursor to the right, holding down the shift key if you want a perfectly straight line.
As you can see you have now created the start of your blend.
Go to your next layer, press the layer mask tool and repeat the above step and do the same for your final layer.
Congratulations, you have now created your blend
Hope this made sense!