i'm sure lots of folks here have built step-up or boost converters ... I guess no one felt like replying to your query.
I've built many small boost converters, probably the largest is taking 3.3v and boosting it up to 5v, only around 5 watts however. most of mine aim for a higher voltage at a rather low current, like 30v at 15mA for a big string of LEDs.
I tried once using a PIC as the brains of a 'digital smps', and it was fun, but my programming skills aren't that great. I leave the smps controlling to dedicated chips and regulators. One of my favs is TI's TPS61040. It has a tiny SOT23-5 package and contains it hefty 400ma switch (iirc), all you add is a diode, a few small caps and the feedback circuit (voltage divider or current sense resistor).