For a few of these, there are quick forms to fill out and you need to make sure you pay attention to the submit by date! I've forgotten a time or two myself, lol.
The Fictionator's Teaser Monday
PicTease on Mondays
A Different Forest has a teaser campfire every Monday
Edwardville (LiveJournal community) has a Teaser thread every Tuesday
The Twigasm's Teaser Tuesday
The Twilight Awards TwiFicBites are posted on Wednesdays
TwiFicNews' Teasers Unplugged are posted on Thursday
Another good way to get your story out there is to take advantage of the different Twitter services/accounts that will shout out a Tweet whenever you update.
TwiNetwork has a great feature called Tweet Me where you sign up and whenever you update, you're given three stories to Tweet. In turn, when another writer updates, someone will be given your story to Tweet about. There are also sections for your Completed Fics and One Shots as well.
The Twilight Awards also has Fic Update Tweets, but it's only available to their Twitter Followers. With almost 5000 followers, I'd say it would be worth it. They also have an Under the Radar section. If your fic is under 750 reviews, with less than an average of 30 reviews per chapter and at least 5 chapters posted, you can submit it to possibly be featured there. Qualifications are listed on the form/application.
TwiFicPromotions also has a Tweet a Fic feature. (They've recently announced that they're merging with The Twilight Awards, so I'm not sure of this will be continuing in the future.)
The Wayward Pushers also have a Tweet My Update Feature, as well as some other cool things that might help you out along the way.
~ If you know of anywhere else, please share! ~