I was too lazy to chart/temp. Also, having a little one meant I had to get up often w/o having lain down for 3 hours straight.
So I used a kit called 'Persona'. A pal bought it off earlypregnancy.co.uk, but fell pregnant before even unwrapping it, so I bought it off her.
Got pregnant the first month I used it! But could easily have used it for birth control.
Thing is, temping and charting works great if you're got a regular cycle, but has definite weaknesses if you don't, so you may wish to use an alternate form of birth control for the first few months of charting.