We have registered our Web Application under the url http:\intranet. We no longer wish to use that URL at all and want to use http:\somethingelse. Is there anyway you can change the default URL in SharePoint?
Even though you can do this by modifying Alternate Access Mappings in the long run you'll be better off by deleting the old web app, but not the databases, add a new web app, activate all needed web app scoped features and attach all the old content databases.
Yes you need to use alternate access mapping for this.
Below links will get you started
I've had to do this in the past with host-named site collections.
We used this MSDN article to get create the site collections: http://technet.microsoft.com/en-us/library/cc288637.aspx#section1
In order to rename them afterwards you can use 'Set-SPSite' to rename them (http://technet.microsoft.com/en-us/library/ff607958).
I did run into one issue using this command related to the web.config file for the web app and a custom login page, but it was a pretty simple solution (http://sharepoint.stackexchange.com/questions/29630/i-am-trying-to-rename-a-site-using-set-spsite-command)