I often use a simple CMOS PLL, using the 4060 for the reference oscillator (with a standard crystal, usually 4MHz) and reference divider, a 4040 as a preset divider (programmed with diodes), and a 4046 for the phase comparator, loop filter and Voltage Controlled Oscillator. The 4046 gives a squarewave output, and the mark / space ratio is somewhat proportional to the frequency, so if I want a really accurate 1 : 1 mark / space ratio, I generate twice the output frequency, and then use a 4013 or 74HC74 bistable to guarantee the waveshape.
The whole CMOS PLL fits on a tiny PCB (really tiny if you go for the Surface Mount versions), uses a standard crystal (I frequently use 4 MHz because I have a boxful of them!) and is easy to set up. It costs just a couple of £ in parts, and will generate any frequency I want.
There's an even simpler version for mediumwave - a 40103 preset divider, 4060, a 4046 and a 4013. The crystal is a 4608 kHz (baud rate generator crystal) which is cheaply available from Farnell / Newark and many other suppliers. This gives 9kHz steps (for Europe. If I want 10 kHz steps, I have to use a 5120kHz rock.
My current cheap MW rig uses the 4-chip synthesiser, driving an IRL-series FET (logic level input), and is modulated by a really simple series modulator, using a TDA2040 IC as a "power op-amp". This basic design is capable of ~20 Watts carrier / 80 Watts peak, and sounds really good on the air. The most expensive parts are the heatsink and the mains power supply. It's not super-efficient, but it's simple and cheap!