DotNetNuke 4.8 added Human Friendly urls, but unlike Friendly URLs, it can only be enabled through the web.config. To enable human friendly urls, replace:
<add name="DNNFriendlyUrl" type="DotNetNuke.Services.Url.FriendlyUrl.DNNFriendlyUrlProvider, DotNetNuke.HttpModules" includePageName="true" regexMatch="[^a-zA-Z0-9 _-]" />
with:
<add name="DNNFriendlyUrl" type="DotNetNuke.Services.Url.FriendlyUrl.DNNFriendlyUrlProvider, DotNetNuke.HttpModules" includePageName="true" regexMatch="[^a-zA-Z0-9 _-]" urlFormat="HumanFriendly" />
UPDATE: In DNN 7.x, DNN incorporated the URL Master functionality for much improved URLs. To enable this, you should now use "advanced" rather than human friendly.
<add name="DNNFriendlyUrl" type="DotNetNuke.Services.Url.FriendlyUrl.DNNFriendlyUrlProvider, DotNetNuke.HttpModules" includePageName="true" regexMatch="[^a-zA-Z0-9 _-]" urlFormat="advanced" />
NOTE: Keep in mind though that no 301 Redirects for existing URLs are created so if you implement this for a site that has been around for awhile, you should make sure to manually create 301 Redirects or set up Canonical URLs for all existing pages to make sure to not dillute your link juice.