All appendix material must be referred to in the main body of the dissertation or it will be ignored. Appendices can become a dumping ground for material that you cannot fit into the dissertation. Remember it is quality not quantity that counts! They can be useful for information that is too detailed or not sufficiently relevant for the main dissertation.
If the research involved gathering primary data the APPENDICES often contain a copy of the interview or postal/e-mail questionnaire (the data collection instrument), the raw data collected such as transcript of a face-to-face interview or a listing of the computer software.