The most well known and best priced supermarkets are listed below.
Migros and Coop are the two big players in the Swiss supermarket scene, with a good reputation in environmental questions. Migros and Coop offer almost everything: from food and household articles over mobile phone and bank services to petrol stations; Migros does not sell alcohol. Have a look at the low-budget lines in their assortments: "M-Budget" at Migros and "Prix Garantie" at Coop. Both Coop and Migros are cooperatives. Aldi, Denner and Lidl are discounters with a smaller product range.
There is no fixed rule in Switzerland regarding opening hours. In general stores are open from 8/8.30 am until 6.30/7 pm and on Saturday until 4/6 pm. In small towns and villages shops are generally closed between 12 noon to 2 pm. Once a week most of the shops in larger cities are open until 8/9 pm. Some filling stations sell food and drinks until 10 pm every day. On Sundays and Monday mornings stores are often closed. You can do some shopping on Sundays at major train stations.
Post offices are usually open from 8 am to 12 noon and from 2 pm to 5 pm on weekdays. On Saturdays, post offices are open from 8.30 am to 11 am or 12 noon. All post offices are closed on Sundays.