LCDs Char/Graphic, I2C chips, 1WIRE chips, Keypads, RC5, RC6, Buffered H/W UARTs, S/W UARTs, SPI and much more. Plus there are more than 140 examples.
Perhaps you will be kind enough to provide links to the Arduino equivalents
BASCOM and the Arduino environment are not directly comparable. Arduino is a SIMPLIFIED development environment for (essentially) non-programmers. The nearest equivalent for comparison would be a full AVR/gcc environment with whatever libraries are out there for "full" AVR/GCC (depending on what level of support you'd like, of course), or a full-fledged commercial C compiler with libraries. It's part of the power of the Arduino that such alternatives (including BASCOM) exist; you can't get an alternate compiler for a basic stamp.
BASCOM does not appear to be compatible with Stamp Basic (it aims at QuickBasic, which is much closer to a standard basic. Stamp basic is lovely in its own right (rather like arudino), but it's not very compatible with anything...)
(and where's my Linux and MacOS versions of BASCOM?)
And the examples cheat (even when they don't have to - I'm sure BASCOM will do much better than Arduino just because of the current "chunkiness" of the arduino libraries: "look: our code is smaller than code from an environment that doesn't try to minimize size!" Duh.)