I had an idea a while ago, and ran it past my co-creator, so it's a go. I propose an alliance.
More than a dropdown and less than a formal crossover, an Alliance would be two to six loosely joined webcomics. They would naturally be fairly similar in content and style, to attract the same type of audience.
The writers/artists would benefit because this gives us a way to get to know each other, perhaps pick up tips, have someone natural to ask about crossovers and guest art, and expose each others' fans to each other.
The fans would benefit because they get more comics that they're interested in, without having to look. We were personally thinking of collecting updaters on all five days of the workweek, so our fans get weekday daily comic goodness. Or you could ally with others who update the same day you do, and form a short webring. Imagine all your fave comics without having to drop down your favorites list.
Naturally, we plan to be fairly picky about our allies. We may wind up rejecting some wonderful people just because we don't think the comic is a good fit, and we are probably going to be rejected ourselves. But nothing ventured, nothing gained, right? I think my idea of allies is a pretty good one, and even if you don't want to ally with us, feel free to post here anyway and see if you can find someone else.