Your ear can be plugged on the inside or on the outside. If doing the valsalva technique (plug your nose and blow, as if to equalize) helps, it is likely on the inside in which case you should see a medic - there is fluid inside your ear, and this often leads to an inner ear infection (or is caused by an inner ear infection). This remedy helps in the case of your ear being plugged on the outside, and for general ear maintenance:
I used to get regular ear infections (outer ear) after diving. Finally, one physician told me that he could prescribe me (more) antibiotics, but he instead suggested a remedy for what he called "swimmer's ear." Similar to emoreira's concoction, it is:
1/3 vinegar, 1/3 rubbing alcohol, 1/3 water
the 1/3 water seems to go a long way in not burning your ear. Lay on your side, apply to one ear, dropwise, let it sit for five minutes, flip over onto the other side, and repeat. Done at the end of a day of diving, it is a brilliant (non-antibiotic) way of keeping your ears healthy. A year later, I am still antibiotic free.