You may already know when you are filling in a URL with the iPhone if you hold down the .com button for a few seconds you are offered selections of .net and .org, but you might not know other keys do the extra-bit-on-hold too.
I was just testing out the next version of my XiaoCiDian iPhone application and found that other keys offer other options when you hold them down. Mostly vowels and and a few punctuation key. Here are some screenshots:
There are many more, but I think you get the picture.
I am not sure if I have these because I have multi keyboards on, but worth a shot. ¿Who doesn’t like to use the upside down question mark?