Make quick side-by-side video mash-ups using YouTube Doubler. Be warned: as with many sites featuring user-generated content, this site has a lot of inappropriate and immature mash-ups in its "Top" and "New" lists.

The site has a simple interface where you enter the links of two videos.  You also have the option to include a starting timecode marker for each video. Anyone who opens the link (generated in the address bar) will be taken to page with the two videos playing simultaneously side-by-side at the starting points you entered.

If you want to avoid sending people to the actual site to view a mash-up, you can embed the mash-up as I did above using the html code. Unfortunately you have to start the videos on your own, and they do not loop automatically as they do in the YouTube Doubler site (see here). 

Note: I also did a find and replace in the html code on the video dimensions in a text editor program (Notepad) to make the embedded videos fit within my website layout.

This week I am in Cape Cod with my wife's family, including our two toddler nieces.  They have enjoyed playing with my iPad (supervised of course) and I have enjoyed seeing which apps they like interacting with the most.  Here are two they have liked so far:

iWriteWords (Free)
I wrote about this app that I learned about from Seth Bowers.  My 2 1/2 year old niece really enjoyed tracing and identifying the letters.  The only part she needed help (i.e. she didn't understand it) with was tilting the iPad so that the letter blocks fall into the "vortex."

3D Drum Kit for iPad ($2.99)
I got a couple of iTunes gift cards for my birthday, so I have been purchasing more apps than I normally might.  The ones that I have been most interested in are the musical instrument and production applications.  Both my 2 1/ year old and 20 month old nieces have liked smashing this drum kit.  It has an easy to use recording interface and a couple of different drum kit sounds.  The drum kit is animated, unlike other drum kit or drum pad apps that just play the sounds.