This is especially difficult when you want to link to something not yet published... like the book itself. Or the next book in your serial. Add in that pre-orders have to have their final draft uploaded 10 days prior to publication and the problem reaches critical mass.
Solution #1: Throw up hands, point everything to a single page on your website, and be done with it.
This has the merit of simplicity. However, your backmatter is the single most strategic advertising space you will ever have: it grabs readers right when they've finished reading your stuff and pitches the next book to them, complete with links to make it one-click buying (vs. wading through your website to see what they want).
Latest version of the backmatter in Open Minds
Solution #2: Use the "funnel" method (get Write.Publish.Repeat for more about this)
Basically you set up one book to lead to another and so on... and never go back to update the backmatter, you just move forward with the next book.
SIDEBAR: Using SMARTurls
I used bit.ly for a long time, but once you make a link in bit.ly you can't ever direct it somewhere new. This is very limiting! SMARTurls work much better because 1) you can change the destination of your link after you've created it, and 2) SMARTurls will redirect based on the user's location (which is great for spurring international sales).
How this works:
1) I'm publishing a new book. I want to put a link to review the book in the backmatter, but I haven't published yet (chicken-and-egg problem). So I create a link called smarturl.it/NEWBOOKonAmazon and point it (temporarily) toward my author page on Amazon.
2) I publish the book
3) Once the book goes live, I redirect smarturl.it/NEWBOOKonAmazon to point to the real book link on Amazon.
This works fabulous for preorders as well, since you have to upload those 10days ahead of publication, and there may be all kinds of links that will be live then but aren't live now. You can use this for other things too - blog posts, facebook posts, anything that will be live in the future, but for right now you need to hand out the link to people to get them started.
The best part: you never have to update the link in your backmatter.
Solution #3: Use modified "funnel" method with some "evergreen" material plus frequently update backmatter in high-selling books - THIS IS THE METHOD I USE
For the most part, I "funnel" readers of one book to the book they're most likely to read next. Then I introduce them to my other works (with a short or long pitch, depending), then I give them a blanket "evergreen" summary of all my works - although that will have to be updated over time as well. Most of my books, I do this once and let it go out of date, but for my highest-selling books, I will frequently update the backmatter. Why? Because that's my most valuable ad real estate, and I use it like I use any ad - keep it fresh and interesting.
Here's the extended version of my backmatter in Open Minds - that book is downloaded a lot (because it's free), so it's high-traffic ad space. I use it to the max! Does everyone read all of this? No... but I only update the version on Amazon and the traffic justifies the bother. My 80/20 rule says it's worth doing.