I personally don't like parking at all, except for really good typein domains, and even for those develloping a site is better.
The reason is simple: Search engines don't like parked domains (using a parking service displaying relevant ads) and any age bonus is lost once the crawler finds the domain parked. So, if you registered a domain in 1999 and park it today, the odds are high that google will treat it like a totally new domain once you or a buyer decides to use it.
Parking can hurt the value of a domain, especially if it's not a typein domain and you miss alot of search engine traffic.
For domains I don't use, I put up a page with some text, ads, links relevant for the domain name. No design, just some stuff you can create in a html editor within 10 minutes. Then I interlink the domains by niche/topic, building little networks and link them from "real" sites, so search engines can pick them up.
I got loads of these placeholder sites, most PR1-3. Build, forget, wait and enjoy the search engine traffic while you look for opportunities to devellope them or sell them. Every shit you build in a few minutes is better than a parking service.
