I had some dust specks on my images (I use a D90) so I decided to buy a sensor cleaning kit from Orient Photo. I spent almost 2 hours cleaning the sensor with swabs.
I was scared at first to apply too much pressure on the sensor but after a while my confidence increased. The swab handle is flexible afterall and is made of plastic so away I went and swabbed the sensor up-and-down, left-and-right.
After 5 swabs and numerouse white-paper tests, all the specks are now gone from my images. I'm a bit worried that I might have damaged my sensor from the repeated scrubbing but I take comfort in Thom Hogan's article on sensor cleaning.
He mentioned that "First, don’t be put off by Nikon’s disclaimers (both Fujifilm and Kodak endorsed user cleaning that touches the sensor if done properly). The Lithium Niobate filter over the Nikon sensors is somewhat difficult to scratch if you use the right tools (on the MHOS Scale of Hardness table that ranges from talc at 0 to diamond at 10, Lithium Niobate is a 5, the same as Apatite, and a bit lower than Orthoclase and Quartz; Fujifilm and Kodak don't identify the material they use [nor does Nikon on the latest cameras], but it seems just as durable). While it's possible to scratch the filter surface, it's also not at all easy to do if you're using the right tools".
I just want to share this to others having dust problems on their DSLR cameras. Scary as it may seem, cleaning your sensor becomes easy once you're confident enough and know what you're doing. If not, send it over to the service center for a fee.