Retinol-A gel is good for surface scarring, you can have it prescribed by your GP. It's worked for me in the past. Dermatix is another gel that is said to improve more significant scarring, I've read about people using it for acne marks but I've not personally tried it so couldn't comment on results. It's like £30 a tube though so maybe not one to risk buying without doing more research.
I used to have very bad acne, I was offered Roaccutane but didn't like the sound of the side effects at all. I chose to have N-Lite laser treatments and glycolic peels instead, very expensive but so worth it. Both have totally changed my skin around - it looks brand new, you'd never know I'd had problems. I hardly break out now and when I do it clears up really quickly. Only way to help the appearance of icepick or indented scars is to use injection fillers.
A totally at home, inexpensive treatment to do would be the aspirin mask - just make sure you're not allergic to aspirin first. The mask helps improve blemishes, redness and controls oil production. Aspirin is made from salicylic acid or BHA which is an exfoliant and also an anti-inflammatory, it's in a lot of acne products. You use 2/3 dissolvable aspirin tablets, add 1/2 a teaspoon of water and wait for the texture of the mixture to go grainy. At this point add some thick honey to help the mask adhere to the face better, then begin application. Avoid the obvious areas such as the eyes, nostrils and mouth and leave for 10 minutes maximum - aspirin is acidic don't try leaving it longer. Rinse your face with warm water whilst rubbing the mask around your face in circular motions. Once all of the mask if removed, use a toner and then moisturise. It's best to repeat this process about 3 times a week. It's certainly not something to do everyday. Although it's not dangerous as a negligable amount of aspirin is actually absorbed into the skin.