Here's one possible solution using an experiment environment: the environment places a title of the form Experiment # with a style similar to that of the standard sections, using a counter that resets with every new chapter; the environment also produces an entry in the ToC. However, the entry will appear where the environment was used (otherwise, as Unapiedra mentioned in a comment, the order in the ToC would be strange); if you want the entries to appear at the end of the entry for a chapter, you'll have to use the environment exactly there.
\documentclass{book}
\usepackage{lipsum}% just to generate text for the example
\newcounter{exp}
\renewcommand\theexp{\thechapter.\arabic{exp}}
\newcommand\experimentname{Experiment}
\makeatletter
\@addtoreset{exp}{chapter}
\makeatother
\newenvironment{experiment}
{\clearpage
%\phantomsection % un-comment if hyperref is to be used
\stepcounter{exp}
\addcontentsline{toc}{section}{\experimentname~\theexp}
\noindent{\Large\bfseries\experimentname~\theexp}%
\par\vspace*{2.3ex plus .2ex}\noindent\ignorespaces}
{\clearpage}
\begin{document}
\tableofcontents
\chapter{Test Chapter}
\section{Test Section One One}
\lipsum[1]
\begin{experiment}
\lipsum*[1]
\end{experiment}
\section{Test Section One Two}
\lipsum[1]
\begin{experiment}
\lipsum*[1]
\end{experiment}
\end{document}
Another option would be to create a new List of Experiments, similar to the standard "Lists of...". Here's how this can be done:
\documentclass{book}
\usepackage{lipsum}
\newcounter{exp}
\renewcommand\theexp{\thechapter.\arabic{exp}}
\newcommand\experimentname{Experiment}
\newcommand\listexperimentname{List of Experiments}
\makeatletter
\@addtoreset{exp}{chapter}
\newcommand\listofexperiments{\chapter*{\listexperimentname}\@starttoc{exp}}
\makeatother
\newenvironment{experiment}
{\clearpage
%\phantomsection % un-comment if hyperref is to be used
\stepcounter{exp}
\addcontentsline{exp}{section}{\experimentname~\theexp}
\noindent{\Large\bfseries\experimentname~\theexp}%
\par\vspace*{2.3ex plus .2ex}\noindent\ignorespaces}
{\clearpage}
\begin{document}
\tableofcontents
\listofexperiments
\chapter{Test Chapter}
\section{Test Section One One}
\lipsum[1]
\begin{experiment}
\lipsum*[1]
\end{experiment}
\section{Test Section One Two}
\lipsum[1]
\begin{experiment}
\lipsum*[1]
\end{experiment}
\end{document}