Hypermedia Glossary of Genetic Terms
You can search for genetic terms or look through a list of 400+ terms. Very helpful. Also links to related terms.

Dictionary of Cell Biology
More extensive than the previous glossary but tends to use techno jargon. Do a search and get a long list of results. Works very well.

DNA to Protein
If you enter in a codon, it will spit back the correct amino acid. Also has some interesting things with mutations. Need javascript on for this.

Knowledge by design
Teaches by example. Very well done site with great graphics. Need things like Quicktime, Flash, Shockwave, and a MPEG movie viewer to see them.