Your course of action really depends on how much work and effort you can put into the expired domain. If you're barely able to maintain and optimize your current site, you probably want to just 301 redirect the old site (note: see my amended comment above about the link value not likely to be passed). If, however, you're more creative and have some time on your hands, you can try your hand at crafting a microsite. If you really know your stuff and are experienced at making money off various websites, you'd probably do well with the third option.
By strategically buying expired domain names which have certain quality features, you can create a link "pump" to your target sites. From an SEO perspective, this can turbo charge your rankings on Google and other search engines. Also, you can make money directly by promoting products on high ranking search results. Additionally, you can make money by selling links on your network to people looking to get an SEO boost.
Regarding my statement above, “Any domain name that reaches expired status and is not renewed by the owner will be auctioned by an auction service.”–it did overstretch. I’ve modified it to be: “A domain name that reaches expired status and is not renewed by the owner will be listed at an auction service (see FAQ for exception to this rule).” Then I added a FAQ to clarify. Please check my thinking:
The way this list is implemented means I can't update prices, nor removed sold domains automatically and sedo doesn't provide me with the tools I need to implement it properly. Unfortunately some users keep contacting me to update their domain prices or remove their domains and I can't keep doing that manually. So I've decided to disable the list for now.