are there any websites that have a 100% chance of actually getting me some millibitcoins?
yes, you can earn bitcoin online on various sites including the bitcointalk forum.
all of it is work and costs some time.
faucets - say 0.00009867 per day for completing all of them. do it for one month and you have 0.002 BTC
signature campaign - anywhere between 0 and 0.4 BTC (As far as I've seen)
sell goods - if sold - still a chance in it
exchange - buy bitcoins using usd or other, example
btc-e.com and
bitstamp.comalso keep an eye on the project section and services section, sometimes they give a lot of btc for tasks.
Apart from these, you can also sell services (eg. coding, translation) or claim some bitcoin giveaway in the "Games and rounds" section.