Vclaw
5
Firstly, not all possible tags are listed on the Map Features page. It is worth searching the wiki, to see if there is anything relevant. Also check Taginfo to see what is in use.
For travel agents and estate agents, they are classed as offices, which is a separate section on the Map Features page. Also see http://wiki.openstreetmap.org/wiki/Key:office The recommended tags are office=estate_agent and office=travel_agent
For photograhpic shops (Jessops etc), the tag is shop=photo. See http://wiki.openstreetmap.org/wiki/Tag:shop=photo
For appliances stores (Comet, Currys), I think shop=electronic is used for this. See http://wiki.openstreetmap.org/wiki/Tag:shop%3Delectronics Though it is perhaps a bit inaccurate, as a cooker does not necessarily have any electronics in it (though most modern ones probably do).
For CD/record shops (eg HMV), I’m not sure if there is a common tag. Just shop=music is confusing with shops selling musical instruments, or sheet music etc. And HMV sell DVDs/games etc as well.