I'll admit, Frost is probably my shakiest tree, if only because I had way too much fun with Unholy and Blood to tear myself away from them too long. Since Blood brings heightened healing and Unholy brings nice AE DPS, Frost also seems to fall behind a bit in the solo department. Still, there are some Death Knights who swear by it, and if you're thinking of leveling Frost, consider a build something like this 18/53/0 Build -- Once again, you'll probably want to focus primarily on the Frost Tree before filling out Blood.
This build allows you to switch very nicely between AE and Single-target DPS. You'll essentially replace Obliterate with Howling Blast and vice-versa to move between the two. You'll also have Frost Strike to dump your runic power, so building up and unloading runic power as quickly as possible is one of the keys to this build's damage. Scent of Blood will help your runic power generation, while Dark Conviction provides some nice synergy with Killing Machine. If you're looking for a quick burst of power, don't forget to use Deathchill.
You can convert this build to a dual wield build in a pinch as well, as long as you can find 3 talent points to put into Nerves of Cold Steel, possibly by dumping Unbreakable Armor and Lichborne, which are nice emergency survival talents, but not absolutely needful if you're focused on grinding and DPS.
Since Obliterate receives so many nice bonuses from this build, getting the Glyph of Obliterate is a good idea for the same reasons it is in the Blood tree, only moreso. Glyph of Frost Strike might be useful if you plan to do a little PvP or AEing, but the chance to freeze is a little too random for my tastes.
Go forth and conquer
We're less than a week away from Wrath, and hopefully all of you my fellow Death Knights are getting strapped in and ready. No matter what method of leveling or what talent spec you go with, I wish you all good speed, and I'll see you at the foot of Icecrown Glacier along with all the other classes -- hopefully sooner rather than later.