As egreg mentioned in a comment, using {\bfseries\small Some text here...\setlength{\parskip}{1em}} won't produce the desired result since the closing brace resets the value of \parskip to what was outside the group. You can use one of the predefined skips (\bigskip, \medskip, \smallskip), or \vspace (also, don't forget to end the paragraph inside the group to get the correct value for \baselineskip):
\documentclass{article}
\newcommand\Text{%
Nam dui ligula, fringilla a, euismod sodales, sollicitudin vel, wisi. Morbi
auctor lorem non justo. Nam lacus libero, pretium at, lobortis vitae, ultricies et,
tellus. Donec aliquet, tortor sed accumsan bibendum, erat ligula aliquet magna,
vitae ornare odio metus a mi. Morbi ac orci et nisl hendrerit mollis.}
\begin{document}
\Text
{\bfseries\small \Text\par}
\vspace{1em}
\Text
{\bfseries\small \Text\par}\bigskip
\Text
\end{document}

\parskipis inserted at the start of a paragraph; the closing brace resets the value of\parskipto what was outside the group. What's the problem with\vspace? – egreg Oct 16 '12 at 22:31\parskipwould be the natural thing to use for separating paragraphs. – jtbandes Oct 17 '12 at 0:49\parskipinside a group makes the change only effective inside that group. – Gonzalo Medina Oct 17 '12 at 2:36