Links to child pages are normally displayed in the sidebar or bottombar only (provided the Pages widget is activated). If you want links to child pages on the parent page itself, then in most themes you have to add them manually.
In the following themes such links show up automatically:
Brand New Day (top of page content)
Fauna (in a changing sidebar)
Misty Look (bottom of page)
Redoable Lite (below page title)
Regulus (in a changing sidebar)
(Also Unsleepable, but only if you don’t activate any widgets.)
In the following themes the standard [*] top nav menu (header page tabs) features dropdowns to child pages:
|
Adventure Journal Autofocus Beach Blogum Bold Life Bouquet Brand New Day Bueno Chateau Choco Chunk Comet Coraline |
Duster Elegant Grunge Enterprise Forever Fresh & Clean Fusion Greyzed Imbalance 2 iNove iTheme2 Inuit Types Koi Liquorice |
Matala Modularity Lite Monochrome Mystique Neutra Nishita Notepad Nuntius Oulipo Parament Piano Black Quintus |
Retro-fitted Rusty Grunge Sandbox 1.6.1 Sandbox 1.6.2 Shaan Selecta Skeptical Splendio Strange Little Town Structure Suburbia Sundance Sunspot |
The Morning After Titan Toolbox Triton Lite Twenty Eleven Twenty Ten Vertigo Vostok Wu Wei zBench |
Notes:
To exlude a child page from showing in a dropdown, you delete its title (after you copy the URL of the page so you can write a link to it where you need it).
Duotone displays tabs to level-one child pages in the header (below their parent).
[*] You can also create dropdowns using the newly introduced custom menu feature – see relevant Support doc for instructions.
Update December 2010: By now all themes with header tabs support custom menus.
wordpress tips 
How do I create a link so that the subpage title will show when I hover over the dropdown parent on the navigation bar?
Posted by Paul Koster | July 16, 2009, 23:09Hi. I’m afraid that’s not possible in free wp.com blogs (assuming you are talking about wp.com). You can only create dropdowns if you buy the CSS upgrade (and know what to do with it). If you’re interested in that, you’ll have to ask at the forum, as I’m not familiar with theme customization. Make sure you give the link to the blog in question – the site linked to your name doesn’t seem to work.
Posted by Panos | July 17, 2009, 02:33I’m having problems with a child page. Perhaps you can advise me.
My site is sbeckow.wordpress.com.
When I create the child page “Silver Birch’s ‘World,” and link it to the parent page “2012 History” and click on the link for the child, I am directed to the parent.
No matter how many times I delete both pages and start again, the same thing happens.
Can you tell me where the error is and how it might be corrected?
Thank you,
Steve Beckow
Posted by Steve Beckow | October 28, 2009, 03:46At the moment “Silver Birch’s ‘World” is a parent page; I can’t tell if and where there’s an error unless you turn it into a child page again.
Posted by Panos | October 28, 2009, 06:34I’ll create a second version of it (“Silver Birch’s ‘New World’ 2” and make it a child to “2012 History.”
By doing that, when you click on the file in the righthand page list, it should bring up “2012 History” instead of “Silver Birch’s ‘New World.'”
I’ll do that now and appreciate your assistance, Panos.
Steve
Posted by Steve Beckow | October 28, 2009, 17:34As a matter of fact, it worked this time.
Hopefully whatever the errors was, it has been corrected.
Thank you for your willingness to help, Panos.
Steve
Posted by Steve Beckow | October 28, 2009, 17:37By any chance, does anyone know if Digg 3 Column has the native (drop down) capability? I didn’t see it in this very useful list but just though I’d ask …
Posted by SamAdams1773 | March 19, 2012, 17:33Does anyone know? I do know, that’s why I made the post. The post lists the themes that support dropdowns in their standard menu. So the free themes that aren’t in the list don’t support dropdowns in their standard menu, so I don’t see the point of the question.
And as my post says, all themes with top navigation support dropdowns if you create and activate a custom top menu.
Posted by Panos | March 19, 2012, 19:37Easy, please. I thought my question was posed very politely& respectfully. One can never be too sure how often (if at all) lists like this – posted 2 years ago – are updated. I just wanted to confirm.
Thank you.
Posted by SamAdams1773 | March 19, 2012, 19:48Make that 3 years ago.
Posted by SamAdams1773 | March 19, 2012, 19:51I usually don’t go easy when I see the wretched question “does anyone”. This isn’t a forum, this is my blog: there are no anyones here.
And since you can count years, you could have gone to Appearance > Themes in your dashboard, click “Newest” to sort themes by launch date, and see that a) Digg 3 is much older, b) my list includes Sundance, Sunspot and Triton Lite, the most recently added wordpress.com themes.
Check the blurb at the top right of my homepage as well:
https://wpbtips.wordpress.com/
Posted by Panos | March 19, 2012, 22:42“And since you can count years”
March 19, 2012 – March 24, 2009 (Posted by Panos ⋅ March 24, 2009 ⋅ 12 Comments ) = 3 years.
You are a gracious one.
Posted by SamAdams1773 | March 19, 2012, 23:03You really can’t read, can you? I didn’t say you can’t count, I said you could have easily found that my lists aren’t outdated.
And you came here because I myself directed you here:
http://en.forums.wordpress.com/topic/trouble-with-hierarchy-pages-their-parents?replies=11#post-843742
If you think that I would direct you to an obsolete list after saying that some WP docs are incomplete or misleading, then you obviously think I’m a moron in addition to gracious.
Posted by Panos | March 20, 2012, 06:16Yes, I did misread your post. Forgive me if you can.
In reference to your March 19, 2012, 19:51 post, there are 2 points, Panos:
1) Before you lay into a an innocent poster for daring to ask “does anyone” and then chiding “This isn’t a forum, this is my blog: there are no anyones here.”, consider that nowhere on this page is it at all obvious that this is “your” site and that YOU are the only one who responds to posts. Most fora like this are quasi-community oriented, where questions and responses are pooled.
2) The list of themes above appears in a 24 March 2009 post (3 years old) and there is no indication that the list is updated with any frequency, or at all. In similar situations on similar posts, there is every indication that the list may be stale. That is why I asked the question about DePo Masthead. The documentarian in me says that the list should have an attribute that tells the viewer when it was last updated (something more recent than 03/24/09). Such a note would obviate this entire discussion.
I never called you a moron.
However, you seem rather thin-skinned and you’re running your site – at least this page – like the Soup Nazi (Seinfeld). Please lighten up.
Posted by SamAdams1773 | March 20, 2012, 16:23Right. Now tell the documentarian in you to go to the top of the sidebar and check AUTHOR, singular, and avatar, singular.
Posted by Panos | March 20, 2012, 23:30