I have found that as each bill arrives, I get rid of the main envelope, the ads and any other parts I won't need when making them out. I keep all of my bills together and then early in the morning when I have a few of them gathered up, I write out the checks, stamp them and seal them.
Then I use a post it note and write the date it is due, the date to mail it and the amount, so I have it for quick reference. This has helped me a tremendous amount! I actually keep mine in my drawer at work and every morning I check to see if I have to mail anything out that day! It also makes things easier because I know ahead of time I can stretch it and pay it online, etc.
I haven't had to sit and do bills longer than about 2 hours a month-total-for almost 2 years now!
This is a fabulous system, the key is to pay attention to location. When putting the mailing date, I make sure to allow for ample time to get there, but it is refreshing to look in my drawer and see everything that is waiting to post for the next few weeks...