The Blindsight, 5-ft. radius was converted to 3.5 in the SRD (look under Divine feats):
SRD said:
BLINDSIGHT, 5-FT.RADIUS [GENERAL]
Prerequisites: Base attack bonus +4, Blind-Fight, Wisdom 19.
Benefit: Using senses such as acute hearing and sensitivity to vibrations, you detect the location of opponents who are no more than 5 feet away from you. Invisibility and darkness are irrelevant, though you discern incorporeal beings.
As for the Blindsight wild feat (from MotW), it was never officially converted. However, I play a druid with the feat, and my DM and I converted it:
Blindsence [Wild]
Your sences are as keen as the bat's.
Prerequisites: Blind-Fight, Listen 11 ranks, ability to use the wildshape class ability to become a dire bat (Large animal)
Benefit: You gain the extraordinary ability blindsense (as described in Capter 8 (p. 290) of the Dungeon Master's Guide), which operates regardless of your form. Like the dire bat, you emit high-frequency sounds, inaudible to most creatures, as a form of "sonar" that allows you to locate objects and creatures within 40 feet. Since this ability relies on hearing, any circumstances that deprives you of that sence also negates your blindsence.
Special: Developing this ability causes additional cartilageous growth on your ears, making them slightly larger and more prominent than before. This causes no discomfort, nor does it affect you in any meaningful way.
The changes in the feat are primarily due to the changes to the (dire) bat in the MM. In 3.0, bats had very poor sight (limited to 10 ft., IIRC), but they compensated it with their excellent sonar (i.e. blindsight).
D&D 3.5 introduced the split between the blindsight and blindsence abilties, and gave normal (human-equivalent) sight to the bats. Bats now get blindsence 40-ft.-radius.
My druid has had the feat since 9th-level. It's a rather useful feat (hence the prerequisites), but not an overly powerful one, as you still have a 50% chance of missing your opponent in darkness (actually, it's less than 50%, since you roll twice in melee, due to the Blind Fight feat, which is a prerequisite).
The 'Special' bit is flavour only. I liked the idea of my character undergoing a slight physical change due to the development of the new ability.
Another option, if you're a druid and if your DM allows it, is to take the Dragon Wild Shape feat from Draconomicon. It gives you all the Su and Ex abilities of the dragon shape you assume, which includes superior low light vision, darkvision, and blindsence.