Is it okay to vacuum a laptop keyboard? Would it cause any damage?
You can use vacuum cleaner, but make sure your laptop's keyboard doesn't have "pop off" keys that could possibly be sucked up by the vacuum.
A can of compressed air will safely blow dust right out of the little crevices between your keys.
You may want to read this article from LifeHacker.
There are small (usually USB-powered) vacuums that you can use that do not generate enough force, nor have large enough intakes, to suck the keys of the board.
Most laptops keyboards have pop-off keys and a normal vacuum will take those keys right off. Those that have what are sometimes called "chiclet" keys do not generally pop off and should be safe from this particular hazard.
However, a more serious problem is the static charge that the friction from the airflow will create. For this reason it is never recommended to use a normal vacuum for cleaning any computer, ever. Canned air does not create this problem, and there are special electronics vacuums that are properly grounded and use other special components that are much less likely to generate enough of a static charge to damage the sensitive electronic components in a computer. Even these electronics vacuums, though, have no protection against sucking keys off keyboards.
For these reasons, I would recommend against using a vacuum to clean any part of any computer. Canned air should be sufficient for your needs. It's also cheap.