Someone in the Google Help Group asked for ways to do the above. As it will be difficult to answer in the group, I have decided to answer the question in a post in this blog.
Now, let's say you have a blog Digital Photography and you are an Amazon Associate. You want to put a link to a book in the sidebar. What you have to do is to sign into your Amazon Associate account, click "Build Links" and select "Text link".
To do this, it will be best if you have a best if you have a browser like FireFox which have tabbed browsing. You open another tab and surf to amazon.com and put the search term for that book, then click on the book you want to link. Copy the URL from the address bar at the top of the page, go back to your Amazon Associate accoount (in a different tab) where you have "Build Links" already opened. Scroll down to "Build Text Link" and paste the URL you have copied into the appropriate field and then type the description of the link you want to be displayed in the other box (see screenshot below, click to enlarge):
Actually the screenshot showed the correct field, but the URL and the description I put is not for a particular book, but for a search result. I believe text link to a particular book has a "shelf life", that is, you willl probably get a message "book no longer available" or something like that when the book goes out of print, or used books are not available. I prefer to link to something like a search result page. I have a demonstration blog Digital Photography Articles and for this post I am going to demonstrate a link to a search result page for "digital photography". I opened a third tab and surfed to amazon.com. There I typed in the search term "digital photography" and got a Digital Photography Articles search result page. Instead of an URL for a book, I thus have an URL for a search result page with many different products related to digital photography, and as long as Amazon has digital photography related products, this will never be a "dead link" and I don't have to worry about checking the link to see if it leads to a "product not available" message or something like that.
(to be continued, with some editing of the above plus further explanation. Got a meeting to attend)