varindent – Make paragraph indentation match the length of the line above
The package will cause paragraphs to indent to the same position as the end of the last line of the previous paragraph, unless the resulting position would take you to within 2\parindent of the end of the line.
Maybe you are interested in the following packages as well.
- pdfcprot: Activating and setting of character protruding using pdfLaTeX
- centerlastline: Paragraphs with last line centered, known as “Spanish” paragraphs
- border: Draw a black border around a Plain TeX page
- sober: Makes appearance of standard styles more "sober"