There's plenty of ideas out there, such as the in a hurry system we talked about earlier, where you have a separate subscription for either at the top of the page and preferably down the side of the sales letter that offers people the chance to subscribe to your list, either through conventional means, offering something for the signup, or even through pop-under, which although I'm not a fan of, they're better than popup that detract from your sales letter.
You can also offer your visitors the chance to receive the sales letter in a split format through follow-up if they don't particularly have the time to read the whole thing straight up. Any of these methods beats the conventional, due to the fact that you're not interrupting the sales process. If you feel you're losing out on subscribers you can always create a product purely for resource building like we mentioned above. The only time I'd consider sales to be more important than plopping a dirty great subscription box in front of your visitors and potential subscribers, and this is when you're selling a high ticket item. I'm talking $250 upwards, because to be honest, if you're selling something at this price, the people seeing the product should already have you on their trusted list, and you should already have them on one of your lists or as part as your resources, whether it be your affiliates, customers, long term customers, your mailing list or even your joint venture prospects.