The easiset way is probably to bookmark the pages you visit most often - when you're on the page you want to bookmark, look for the star icon at the top of your browser, clicking on that will 'favourite' a page. (The star icon is the bookmark function for both Chrome and Firefox, but they work a little differently. Not sure about Internet Explorer, or any other browsers, though). You can add individual bookmarks to the browser window for easy access, or access them via a menu.
Personally, I just take advantage of the frequency I visit the discussion boards and simply type a c into the URL bar of my browser and hit enter (the most frequently visited addresses pop up when you start typing a webiste address, and the selling board's url starts with C (for community), so the second I type c, the address is pre-filled with the link to the selling board, so then all I have to do is hit enter to confirm).
The 'Community' link at the bottom of eBay pages takes you to the main page, where the Discussion Boards and Feeback Forum can then be accessed from a menu on the lefthand side.
