Here’s a little tip I haven’t seen anywhere else. MobileSafari auto-completes URLs with .com if you don’t specify a domain. For example, type in “yahoo” into the address bar, and hit Go. MobileSafari will add the leading “http://”, and then the trailing “.com”.
Adding the leading http:// reference is well-known, but I haven’t seen (or found during a search) anyone detailing the .com being added. This may be a firmware 2.0+ addition, but I don’t think so.
Note: This tip is guaranteed to save you milliseconds during your day.