In an effort to help out. I have made this thread detailing status of several toy lines.
Cybertron:
The Cybertron Line is officially over. Whatever you see in Stores, are the last few figures left. and no more will be available at retail. Unless the Store has some in there warehouse they forgot to put out. you're best bet for figures, is Ebay or Online Stores like http://www.hasbrotoyshop.com/, or http://www.bigbadtoystore.com.
Classics:
The Classics Line is also over. although its more likely to find some left overs at brick and mortar stores than Cybertron. Still your best bet is ebay or the online stores, like the ones mentioned above.
It appears that recently some stores have started re-stocking classics. This in no way implies Classics is still going, only that certain stores have stock available, or Hasbro is still shipping the last remaining cases of Classics. Buy what you want now, as its most likely the last re-stocking of Classics. Such stores include Toys R Us, Wal-Mart, Target in certain areas. This might not be the case in stores near you.
Alternators:
The release of Rodimus marks the end of this line. It is highly unlikely you'll find anything left over in stores. Rodimus is of currently only available through online stores AFAIK.
Titanium:
The 6inch transformable Titanium Line has also come to an end.(Someone correct me if I'm Wrong please) WWI Prowl, and WWI Grimlock are the last moulds to see a release. Menasor (A Rodimus Repaint) is I believe an online exclusive (again correct me if I'm wrong). There are a few repaints that were shown at Botcon and Comicon, but theres no information so far whether they are to be released or not. Additionally, there were several prototypes for this line shown, who's status is unknown, probably will not see a release ever, but we hope some of them like Shockwave and Cosmos make it to the Universe line next year.
Movie Line:
As it stands the Movie Line is the only main line currently at retail, and being supplied regularly(or so its supposed to be) There are a few more waves yet to come in the following months.
The Next major toy line to be released is Transformers Animated. There's still a little discrepancy on actual release dates. So far some places say it will be released in Spring of 2008. Other's believe they will be released earlier than that. We have no actual specific date so far for there release.
EDIT: The Cartoon has been given a tentative Release Date of December or January of 2008. Thanx to Overloaded for pointing this out.
There will be a new line, following in the style of the now defucnt Classics. It will be called Transformers Universe, and is scheduled for release in Fall of 2008. The only characters that have been confirmed for this line thus far, are Sideswipe, Sunstreaker, and Octane (triple changer).
That is all for now. If there is new info on the status of the newer lines, or actual release dates, I'll probably update this thread with them, if it hasn't disappeared into the oblivion that is page 2 of the forums.

If anybody find anything that is not accurate please tell me and I'll correct it. If you wish to add something , please feel free to do so.
EDTI: Renamed.
EDIT: Thanx To Scaleface, for providing additional info on availability of figures of the mentioned lines:
Scaleface wrote:Here are some links for those still trying to get figures from the lines mentioned in the first post:
Cybertron:
Hasbro Toy Shop still have about 19 different Cybertron toys in stock, including show characters like Backstop, Brakedown, Lugnutz, Clocker, Dark Crumplezone and Metroplex. They also have the character of Smokescreen which is everything short of being a "Classics" Smokescreen.
http://www.hasbrotoyshop.com/ProductsBy ... 96&SBR=319
Classics:
Cliffjumper, Mirage and Optimus Prime are all in stock on the Hasbro Toy Shop.
http://www.hasbrotoyshop.com/ProductsBy ... 96&SBR=438
Alternators:
Rollbar is still on the Hasbro toy shop.
http://www.hasbrotoyshop.com/ProductsBy ... 96&SBR=167
6 inch Titaniums:
RiD Optimus, Optimal Optimus and Scourge are on the Hasbro Toy Shop.
http://www.hasbrotoyshop.com/ProductsBy ... 96&SBR=524
Movie:
6 Deluxes still on Hasbro Toy Shop (the 2 protoforms, Jazz, Brawl, Wreckage Scorponok).
http://www.hasbrotoyshop.com/ProductsBy ... 96&SBR=502
Plus Ratchet.
http://www.hasbrotoyshop.com/ProductsBy ... 96&SBR=502
Scaleface's Original Post is in the third page of this thread.