We've found that Arkham Horror tends to have the opposite feel that it should - in the begining, there is a frantic rush to seal gates. Later on once you have a few gates sealed, you can move at a very relaxed pace. In fact, it often becomes apparent there is no way for Old One to appear at all, since there aren't really enough gate locations to build up enough Doom tokens, which also leads to the problem that its actually very BAD to close (without sealing) a gate, since it just lets more Doom tokens appear!

We tried changing things a bit, and really liked how this worked out.

Edit 8/2009: This variant has changed over time, and since people keep occasionally ask about the 'StormKnight' variant or look for it, I thought I should keep it up to date. However, after much debate and more plays, we're back to the good old original version! We found this does work fine with Dunwich.

When you draw a gate at a location with no gate, place a gate and a monster as usual, but DO NOT add a Doom token.

When you draw a gate at a location with an active gate, add a monster at the location and ADD a Doom token, but do not place extra monsters.

When you draw a gate at a sealed location, do not place a gate or doom token, but place one monster at every open gate (as you would have when a gate opened where there already was an existing gate in the normal rules). (This represents dark forces mobilizing in direct response to your investigator's efforts).

This seems to nicely alter the flow of the game. Early on, the Doom isn't building up, and you can actually afford to close gates. As more gates build up, the Doom track builds up faster. Seal gates, and its a big boon - but you will face more of a threat. And there's never a "safe" point where you know the Old One will never appear.

Edit: Whoops! Forgot to mention a minor thing. We did start out the doom track with one token on it.

More Edits: Our other standard house rules are:
1) If it comes to a battle, the GOO receives 7 extra doom tokens -2 doom tokens for each sealed gate. So if you have 2 seals, the GOO has 3 extra doom. If you have 5 seals, it has 3 less doom than normal.

2) We don't remove allies as the terror track increases. Instead, when you get to freely recruit an ally, draw a number of allies equal to 10 - the terror level and pick from those drawn. For the rumor that removes allies, start a marker at the terror level and move it upwards for each terror increase or ally discarded - if it hits 10, the rumor is failed.

Another Edit: Just for the record, credit for this variant goes a lot (probably more than me) to Nightmare.

Edit 8/09: The following was another variant that was used at some point. Since its no longer in use I've spoiler blocked it out to clearly mark it, but left it for completeness.