The internet is a fantastic tool for landlords to advertise an available rental property. Many sites do not charge a fee for listings, allow color photos, and are read by a lot of potential tenants.
Craigslist is by far one of the most widely used free listing sites. Ads can be detailed and contain pictures (several of the outside and one of each room if possible). The best results are achieved if a contact number is placed directly in the advertisement. Use caution about giving the exact address if the property is completely vacant as thieves and vandals often use these online forums to locate properties to target.
Check local newspapers as there may be discounts for online ads. If this is not the case the next place to go is the local convenience store. Look to see if there is a rack of local printed ad sheets, some common names are Greensheet, I wanta, Ad Weekly, and The Want Ads. Titles will vary from one area to another and may not be offered in some locations but most of these publications contain instructions on how to place an online ad and in many cases it is very reasonable or free of charge. Use a combination of all the available resources to achieve the best results.
Sites such as Yahoo also offer a forum to place a for rent ad, however the cost is $35-$60 for a thirty day listing. If the property is in an area that attracts professionals who are transferred for employment purposes sometimes it is worth the cost for the national exposure.
Don't forget about realtors, they often have heavy traffic websites and will list the property both online and in a printed form. Although fees are much higher than other methods, the realtor can offer a full service package where they will show the property and find a tenant.
What about an individual website? This can only work if traffic can be driven to the site. A small website listing a few rentals will only work if the landlord has a database of prospective tenants who can be notified when properties are or will be vacant. This is very limiting and will have monthly hosting costs for a decent site free of others advertisements. Design work can also be costly if a landlord out sources the job. A small inexpensive site that links to listings elsewhere is most effective unless a landlord has a multitude of properties or owns very large apartment buildings.
When in doubt, get online and start those keyword searches. There is something out there for every situation and budget. Prospective tenants are out there looking for a place to live; thanks to technology it is now much easier to find them.