Can I make one or more posts “sticky” at the top of the homepage?

Yes! You'll need to fork an editable copy of your template, then add the following above the {{#entries}}...{{/entries}} block in entries.html:

<p>Sticky entries:</p>
{{#allEntries}}
{{#metadata.sticky}}
<a href="{{{url}}}">{{title}}</a><br>
{{/metadata.sticky}}
{{/allEntries}}

Then add the following custom metadata at the start of the posts you'd like to make sticky:

Sticky: yes

Please let me know if you have any questions about the above, or anything else!