GOOG splits into two share classes today, A and C, whose symbols are GOOGL and GOOG, respectively. "C shares" do not have voting rights. Why they didn't just add GOOGL as the class C shares and leave GOOG as class A, I don't know. It would have made things too easy I guess.

The current A shares, GOOG will be split by half and will become GOOGL. You'll need to make this adjustment manually in your DataSets. Here's the procedure:

Fidelity Data (WL Pro)
1. Close WLPro
2. Find SymbolQuarantineList.txt in the following folder:
C:\Users\You\AppData\Roaming\Fidelity Investments\WealthLabPro\1.0.0.0\Data\FidelityStaticProvider
3. Open SymbolQuarantineList.txt in a text editor and add GOOG= on a new line
4. Start WLPro, open the Data Manager > Fidelity Data tab
5. Find GOOG in the list, click on it.
6. On the right, change the symbol to GOOGL. This operation can take several seconds, be patient. This will change GOOG to GOOGL in all your DataSets, regardless of the scale.
7. Now open a GOOGL chart, right click and perform a 2 for 1 split for 4/2/2014
8. Repeat Step 7 for each intraday interval that you keep for GOOGL

Non-Fidelity Data
The operations will depend on the provider and it might be best to wait until after the market today to simply refresh GOOG and GOOGL symbols. Morningstar already has this ready (GOOG now has the short history of the class C shares, whereas the full history is preserved in GOOGL). Yahoo! doesn't have GOOGL ready yet.

For trading today, you'll need to split GOOG 2 for 1, and keep in mind that if you owned GOOG before today, you'll now have an equal number of shares in GOOG and GOOGL at half the price.

DataSets
Technically the S&P 100, S&P 100, and Nasdaq 100 will now have one extra symbol, representing both share classes: GOOGL and GOOG. If the two classes of Viacom stock is any guide (VIA and VIAB), GOOGL and GOOG will trade approximately at the same price, with minor differences. I don't see any advantage to added both share classes to a trading DataSet, which would likely result in double exposure to the same company.

More info:
http://www.bloomberg.com/news/2014-04-03/new-google-shares-hit-market-as-founders-cement-grip-with-split.html?cmpid=yhoo

Fidelity Data (WL Pro)
Fidelity didn't "split" the stock history of GOOGL, consequently the data for the most recent 5 days will be "corrected" to the unsplit share price, which will create a nice spike in your charts. To correct it, right click the chart, Reload Price History. Right click again, Process a stock split and then apply the 2:1 split on 4/2/2014. Again, you'll have to repeat this process each day for about 1 week.

If you happen to use the "Relocate Data" feature of the Data Manager, apply the change in the relocated data directory.