Here's a few...
Sore throats (and coughing) can be soothed by swallowing honey straight-up or slightly diluted with warm water with honey to make it easier to swallow. The best time to do this is at bedtime given it will stick around for awhile (eating/drinking will wash away the coating). The purpose of honey is to create a throat barrier to ease the discomfort.
Think of it like chapstick to coat irritated lips, but meant for the throat.
Use of honey is also recommended by the World Health Organization which has also published a monogram on viral colds and the various treatments explained. Pay particular close attention to Annex 3 (Page 11) which gives various recipes to treat pediatric cough including the use of honey.
Effect of Honey, Dextromethorphan, and No Treatment on Nocturnal Cough and Sleep Quality for Coughing Children and Their Parents. Arch Pediatr Adolesc Med. 2007;161(12):1140-1146.
Dry cool air increases risk of viral infections as well as giving it to others. As such, add room humidification to a bedroom and keep the door closed (small room humidifiers can't humidify an entire house... so keep door closed!).
Why does this help? Increased humidification inactivates viruses!
Humidification also helps minimize a persistent dry cough worse at night often due to reactive airway disease triggered by breathing in dry air.
However, keep in mind that if you actively have a viral illness, it is too late for humidity to help. It is best used as a preventative measure.
Dynamics of airborne influenza A viruses indoors and dependence on humidity. PLoS One. 2011;6(6):e21481. Epub 2011 Jun 24. Influenza virus transmission is dependent on relative humidity and temperature. PLoS Pathog. 2007;3:e151.
Heated, humidified air for the common cold. Cochrane Database Syst Rev. 2011 May 11;(5):CD001728.
3) Gargling and Saline Flushes
Gargle with saline water... or even just tap-water on a daily basis. Why does this help prevent viral infections? It washes away the viral particles before it gets a chance to cause problems.
It's also probably why drinking lots of fluids also helps since the viruses get deactivated in the stomach from the acidic digestion.
Unfortunately, gargling only helps with the throat... saline flushes are required to help with sino-nasal problems.
Can we prevent influenza-like illnesses by gargling? Intern Med. 2007;46(18):1623-4. Epub 2007 Sep 14.
This naturally-occurring sugar substitute apparently has all sorts of anti-bacterial as well as anti-fungal properties and has been known to doctors and scientists but hardly marketed or promoted in any fashion.
However, the importance of this compound is that it DOES appear to significantly decrease the incidence of ear infections and sinus infections when used regularly. It comes in nasal spray form as well as gum.
Sometimes the BEST medicine are things you can do at home without need for a physician visit... and is based on fact rather than anecdotal evidence.