Generally, this is going to be more trouble than it's worth if all you're looking for is speed. You're not going to be able to load-balance individual downloads (or uploads, mostly) across the two links; the best you'll be able to do is have some sort of rule that says things like "traffic to network X goes out link A" or "traffic from WiFi device Y goes out link B".
Now, if you have a ton of small connections (say, a business with hundreds of users) then this may actually speed things up. Especially if the two links are similar speeds and can't be upgraded any more. But for normal residential or tiny-business uses, it's just going to make things more complex. You'd be better off with one fast link vs two slower links.
If your connection is especially flaky (or the cost of outages is especially high), then having redundant links and failing over when one is down can be useful, but it adds complexity, and if you don't know what you're doing, you'll probably just end up with a mess that's less reliable than a simple single-upstream network.